CVE-2018-5154 in Firefox
Summary
by MITRE
A use-after-free vulnerability can occur while enumerating attributes during SVG animations with clip paths. This results in a potentially exploitable crash. This vulnerability affects Thunderbird < 52.8, Thunderbird ESR < 52.8, Firefox < 60, and Firefox ESR < 52.8.
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Analysis
by VulDB Data Team • 11/26/2025
The vulnerability identified as CVE-2018-5154 represents a critical use-after-free condition that manifests during the processing of Scalable Vector Graphics animations involving clip paths. This flaw exists within the rendering engine of Mozilla Firefox and Thunderbird browsers, specifically affecting versions prior to 52.8 for Thunderbird and 60 for Firefox. The issue stems from improper memory management during the attribute enumeration phase of SVG animation processing, creating a scenario where freed memory locations may be accessed or reused by subsequent operations.
The technical exploitation of this vulnerability occurs when the browser encounters SVG elements that utilize clip paths within animation sequences. During the rendering process, the system allocates memory for attribute objects that define the clip path properties and animation parameters. When the animation loop completes or is interrupted, the system properly frees this memory but fails to properly invalidate references to the freed objects. Subsequent access to these invalid references can result in memory corruption that manifests as a crash, potentially providing an attacker with opportunities to execute arbitrary code through carefully crafted malicious SVG content.
This vulnerability directly maps to CWE-416, which describes the use of freed memory condition, and aligns with several ATT&CK techniques including T1203 (Exploitation for Client Execution) and T1059 (Command and Scripting Interpreter). The operational impact extends beyond simple browser crashes, as the instability can be leveraged for remote code execution in targeted attacks. Attackers could craft malicious websites or email attachments containing specially constructed SVG files that trigger the vulnerability when viewed or processed by affected browsers, making this particularly dangerous in phishing campaigns or drive-by download scenarios.
The affected software ecosystem includes not only the primary browser products but also their extended support releases, indicating the widespread nature of this memory management flaw. Organizations running these vulnerable versions face significant risk as the vulnerability can be exploited through web-based attacks without requiring user interaction beyond visiting a malicious website. The exploitation requires no special privileges or user actions beyond normal browsing behavior, making it particularly concerning for enterprise environments where users may encounter untrusted web content regularly. Security patches for this vulnerability were released as part of the regular update cycles for both Firefox and Thunderbird, with immediate remediation recommended for all affected systems. The fix implemented by Mozilla addressed the memory management issue by ensuring proper reference invalidation and null-checking during the attribute enumeration process, preventing the use-after-free condition from occurring during SVG animation processing.