CVE-2018-5148 in Firefox
Summary
by MITRE
A use-after-free vulnerability can occur in the compositor during certain graphics operations when a raw pointer is used instead of a reference counted one. This results in a potentially exploitable crash. This vulnerability affects Firefox ESR < 52.7.3 and Firefox < 59.0.2.
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Analysis
by VulDB Data Team • 11/26/2025
The vulnerability described in CVE-2018-5148 represents a critical use-after-free condition within the Firefox browser's compositor component, which operates as a core subsystem responsible for rendering graphics and managing visual elements on web pages. This flaw manifests during specific graphics operations where the application employs raw pointers instead of reference-counted objects, creating a scenario where memory previously deallocated can be accessed and potentially manipulated by malicious actors. The compositor's role in handling complex visual operations makes this vulnerability particularly dangerous as it can be triggered through normal web browsing activities involving graphics-intensive content.
The technical implementation of this vulnerability stems from improper memory management practices within Firefox's graphics rendering pipeline, specifically when dealing with object lifetimes and memory deallocation sequences. When a raw pointer is used rather than a reference-counted smart pointer, the application loses track of object ownership and lifecycle management, leading to situations where an object may be freed from memory while still being referenced elsewhere in the code. This fundamental flaw in memory management aligns with CWE-416, which describes use-after-free vulnerabilities that occur when memory is accessed after it has been freed. The vulnerability affects Firefox ESR versions prior to 52.7.3 and standard Firefox versions prior to 59.0.2, indicating that this was a widespread issue affecting multiple release channels.
The operational impact of this vulnerability extends beyond simple application crashes, as it creates a potential exploitation vector for remote code execution attacks. Attackers can craft malicious web content that triggers the specific graphics operations leading to the use-after-free condition, potentially allowing them to execute arbitrary code with the privileges of the browser process. This represents a significant security risk in the context of modern web browsing, where users regularly encounter untrusted content from various sources. The vulnerability's exploitation potential aligns with ATT&CK technique T1059.007, which covers the use of scripting languages to execute malicious code, as the attack vector involves manipulating browser internals through crafted web content. The compositor's involvement in graphics rendering also means that the vulnerability could be triggered by multimedia content, images, or canvas operations commonly found on modern websites.
Mitigation strategies for CVE-2018-5148 primarily focus on updating to patched versions of Firefox where the memory management issues have been addressed through proper reference counting implementations. System administrators and users should prioritize immediate updates to Firefox ESR 52.7.3 or Firefox 59.0.2, as these releases contain the necessary fixes for the use-after-free condition. Additional protective measures include implementing browser security features such as address space layout randomization, stack canaries, and other exploit mitigations that make exploitation more difficult even if a vulnerability were to be present in an unpatched system. Organizations should also consider network-level protections and content filtering to reduce exposure to potentially malicious web content that could trigger this vulnerability during normal browsing operations. The fix implemented by Mozilla involved correcting the memory management patterns within the compositor subsystem to ensure proper reference counting and object lifetime management, thereby preventing the conditions that lead to the use-after-free scenario.