CVE-2018-5095 in Firefox
Summary
by MITRE
An integer overflow vulnerability in the Skia library when allocating memory for edge builders on some systems with at least 8 GB of RAM. This results in the use of uninitialized memory, resulting in a potentially exploitable crash. This vulnerability affects Thunderbird < 52.6, Firefox ESR < 52.6, and Firefox < 58.
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Analysis
by VulDB Data Team • 11/26/2025
The CVE-2018-5095 vulnerability represents a critical integer overflow flaw within the Skia graphics library that specifically manifests when systems possess 8 gigabytes or more of random access memory. This vulnerability resides in the edge builder memory allocation mechanisms and demonstrates how seemingly benign memory management operations can create significant security risks. The Skia library serves as a fundamental component in Mozilla's browser applications, including Firefox and Thunderbird, making this flaw particularly concerning for widespread exploitation potential. The vulnerability's manifestation is directly tied to the system's memory configuration, indicating that certain hardware specifications create predictable conditions for exploitation.
The technical implementation of this vulnerability stems from improper integer overflow handling during memory allocation processes within the edge builder subsystem of Skia. When the library attempts to calculate memory requirements for edge building operations on high-memory systems, integer overflow occurs, leading to incorrect memory sizing calculations. This miscalculation results in the allocation of insufficient memory blocks, which subsequently causes the system to utilize uninitialized memory regions. The uninitialized memory contains arbitrary data from previous operations or system processes, creating potential for both crash exploitation and more sophisticated attack vectors. The vulnerability operates at the intersection of memory management and integer arithmetic, making it particularly insidious as it leverages fundamental computational principles to create exploitable conditions.
The operational impact of CVE-2018-5095 extends beyond simple denial-of-service scenarios to potentially enable remote code execution under specific conditions. When exploited, the vulnerability can cause application crashes that may be leveraged to execute arbitrary code within the context of the affected browser processes. This represents a significant threat to user security as it allows attackers to potentially compromise systems through web-based attacks. The vulnerability affects multiple Mozilla products including Thunderbird versions prior to 52.6, Firefox Extended Support Release versions before 52.6, and standard Firefox versions before 58. These affected versions represent a substantial user base, amplifying the potential impact of the vulnerability. The exploitation requires specific system configurations with at least 8 GB of RAM, which limits the attack surface but does not eliminate the risk for affected users.
Mitigation strategies for CVE-2018-5095 primarily focus on immediate software updates and patches provided by Mozilla to address the integer overflow in the Skia library. Users should prioritize updating to the patched versions of Firefox, Thunderbird, and Firefox ESR to eliminate the vulnerability. System administrators should implement comprehensive patch management procedures to ensure all affected applications are updated promptly. The vulnerability aligns with CWE-190, which specifically addresses integer overflow conditions, and represents a classic example of how improper input validation can create security weaknesses. From an ATT&CK framework perspective, this vulnerability maps to techniques involving privilege escalation and remote code execution through software exploitation, making it a significant concern for cybersecurity professionals. Organizations should also consider implementing additional security controls such as network monitoring to detect potential exploitation attempts and application whitelisting to prevent execution of unpatched versions.