CVE-2015-4488 in Firefox
Summary
by MITRE
Use-after-free vulnerability in the StyleAnimationValue class in Mozilla Firefox before 40.0, Firefox ESR 38.x before 38.2, and Firefox OS before 2.2 allows remote attackers to have an unspecified impact by leveraging a StyleAnimationValue::operator self assignment.
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Analysis
by VulDB Data Team • 10/22/2024
The CVE-2015-4488 vulnerability represents a critical use-after-free flaw within Mozilla Firefox's rendering engine, specifically affecting the StyleAnimationValue class. This vulnerability exists in multiple Firefox versions including the mainstream Firefox 39.0 and the extended support release 38.x series before their respective patches. The issue manifests when the browser processes CSS animations and transitions, creating a scenario where memory previously deallocated can still be accessed, potentially leading to arbitrary code execution. The vulnerability is particularly dangerous because it can be triggered through web content, making it exploitable in remote attack scenarios without requiring user interaction beyond visiting a malicious website.
The technical root cause of this vulnerability lies in improper memory management within the StyleAnimationValue class, which handles CSS animation values during web page rendering. When the operator self-assignment operation occurs on a StyleAnimationValue object, the memory management logic fails to properly handle the reference counting or garbage collection process. This flaw creates a window where an object's memory is freed but references to it remain active, allowing attackers to manipulate the freed memory through carefully crafted CSS animation sequences. The vulnerability is classified under CWE-416 as a use-after-free condition, which is a well-known class of memory safety issues that can lead to remote code execution when exploited properly.
The operational impact of this vulnerability extends beyond simple browser compromise, as it provides attackers with a pathway to execute arbitrary code on affected systems. Remote attackers can leverage this flaw by hosting malicious web content that triggers the specific CSS animation patterns required to activate the use-after-free condition. Once successfully exploited, the vulnerability could enable attackers to execute malicious code with the privileges of the Firefox process, potentially leading to full system compromise. The attack surface is broad as CSS animations are commonly used across websites, making this vulnerability particularly dangerous for widespread exploitation. This type of vulnerability aligns with ATT&CK technique T1059.007 for command and scripting interpreter, as successful exploitation would likely involve executing malicious code within the browser environment.
Mitigation strategies for CVE-2015-4488 primarily focus on immediate patch deployment and browser updates, as Mozilla released versions 40.0, Firefox ESR 38.2, and Firefox OS 2.2 to address this issue. Organizations should prioritize updating all affected Firefox installations to the patched versions, as the vulnerability has been fully resolved through these releases. Additionally, implementing network-level protections such as content filtering and web application firewalls can provide temporary defense while updates are being deployed. Security teams should also consider monitoring for exploitation attempts through network traffic analysis, as the specific CSS animation patterns used to trigger this vulnerability would be detectable in network logs. The vulnerability serves as a reminder of the critical importance of memory safety in browser implementations and the need for continuous security auditing of complex rendering engines.