CVE-2019-8518 : Détail

CVE-2019-8518

8.8
/
Haute
Overflow
60.27%V3
Network
2019-12-18
16h33 +00:00
2019-12-18
16h33 +00:00
CVE.org
NVD
Notifications pour un CVE
Restez informé de toutes modifications pour un CVE spécifique.
Gestion des notifications

Descriptions du CVE

Multiple memory corruption issues were 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.

Informations du CVE

Faiblesses connexes

CWE-ID Nom de la faiblesse Source
CWE-787 Out-of-bounds Write
The product writes data past the end, or before the beginning, of the intended buffer.

Métriques

Métriques Score Gravité CVSS Vecteur 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]

EPSS

EPSS est un modèle de notation qui prédit la probabilité qu'une vulnérabilité soit exploitée.

Score EPSS

Le modèle EPSS produit un score de probabilité compris entre 0 et 1 (0 et 100 %). Plus la note est élevée, plus la probabilité qu'une vulnérabilité soit exploitée est grande.

Percentile EPSS

Le percentile est utilisé pour classer les CVE en fonction de leur score EPSS. Par exemple, une CVE dans le 95e percentile selon son score EPSS est plus susceptible d'être exploitée que 95 % des autres CVE. Ainsi, le percentile sert à comparer le score EPSS d'une CVE par rapport à d'autres CVE.
EPSS First.org

Informations sur l'Exploit

Exploit Database EDB-ID : 46649

Date de publication : 2019-04-02 22h00 +00:00
Auteur : Google Security Research
EDB Vérifié : Yes

/* While fuzzing JavaScriptCore, I encountered the following JavaScript program which crashes jsc in current HEAD and release (/System/Library/Frameworks/JavaScriptCore.framework/Resources/jsc on macOS): */ // Run with --thresholdForFTLOptimizeAfterWarmUp=1000 // First array probably required to avoid COW backing storage or so... const v3 = [1337,1337,1337,1337]; const v6 = [1337,1337]; function v7(v8) { for (let v9 in v8) { v8.a = 42; const v10 = v8[-698666199]; } } while (true) { const v14 = v7(v6); const v15 = v7(1337); } /* Note that the sample requires the FTL JIT threshold to be lowered in order to trigger. However, I also have a slightly modified version that (less reliably) crashes with the default threshold which I can share if that is helpful. Following is my preliminary analysis of the crash. During JIT compilation in the FTL tier, the JIT IR for v7 will have the following properties: * A Structure check will be inserted for v8 due to the property access. The check will ensure that the array is of the correct type at runtime (ArrayWithInt32, with a property 'a') * The loop header fetches the array length for the enumeration * The element access into v8 is (incorrectly?) speculated to be InBounds, presumably because negative numbers are not actually valid array indices but instead regular property names * As a result, the element access will be optimized into a CheckBounds node followed by a GetByVal node (both inside the loop body) * The CheckBounds node compares the constant index against the array length which was loaded in the loop header The IR for the function will thus look roughly as follows: # Loop header len = LoadArrayLength v8 // Do other loop header stuff # Loop body CheckStructure v8, expected_structure_id StoreProperty v8, 'a', 42 CheckBounds -698666199, len // Bails out if index is OOB (always in this case...) GetByVal v8, -698666199 // Loads the element from the backing storage without performing additional checks // Jump back to beginning of loop Here is what appears to be happening next during loop-invariant code motion (LICM), an optimization designed to move code inside a loop body in front of the loop if it doesn't need to be executed multiple times: 1. LICM determines that the CheckStructure node can be hoisted in front of the loop header and does so 2. LICM determines that the CheckBounds node can *not* be hoisted in front of the loop header as it depends on the array length which is only loaded in the loop header 3. LICM determines that the array access (GetByVal) can be hoisted in front of the loop (as it does not depend on any loop variables) and does so As a result of the above, the IR is transformed roughly to the following: StructureCheck v8, expected_structure_id GetByVal v8, -698666199 # Loop header len = LoadArrayLength v8 // Do other loop header stuff # Loop body StoreProperty v8, 'a', 42 CheckBounds -698666199, len // Jump back to beginning of loop As such, the (unchecked) array element access is now located before the loop header with the bounds check only happening afterwards inside the loop body. The provided PoC then crashes while accessing memory 698666199 * 8 bytes before the element vector for v6. It should be possible to turn this bug into arbitrary out-of-bounds access, but I haven't tried that. Hoisting of GetByVal will only happen if safeToExecute (from DFGSafeToExecute.h) returns true. This function appears to only be concerned about type checks, so in this case it concludes that the GetByVal can be moved in front of the loop header as the StructureCheck (performing the type check) is also moved there. This seems to be the reason that the property store (v8.a = 42) is required as it forces a CheckStructure node which would otherwise be missing. The invocations of v7 with a non-array argument (1337 in this case) seem to be necessary to not trigger a bailout in earlier JIT tiers too often, which would prevent the FTL JIT from ever compiling the function. */

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

Références