CVE-2014-1531 in Firefox
Summary
by MITRE
Use-after-free vulnerability in the nsGenericHTMLElement::GetWidthHeightForImage function in Mozilla Firefox before 29.0, Firefox ESR 24.x before 24.5, Thunderbird before 24.5, and SeaMonkey before 2.26 allows remote attackers to execute arbitrary code or cause a denial of service (heap memory corruption) via vectors involving an imgLoader object that is not properly handled during an image-resize operation.
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Analysis
by VulDB Data Team • 11/25/2025
The CVE-2014-1531 vulnerability represents a critical use-after-free flaw in Mozilla Firefox and related applications that fundamentally compromises memory safety during image processing operations. This vulnerability resides within the nsGenericHTMLElement::GetWidthHeightForImage function, which is responsible for handling image dimension calculations during web page rendering. The flaw manifests when an imgLoader object undergoes improper memory management during image-resize operations, creating conditions where freed memory regions can be accessed and manipulated by malicious actors. Such memory corruption vulnerabilities are particularly dangerous because they can be exploited to execute arbitrary code or cause system instability through heap corruption.
The technical exploitation of this vulnerability leverages the fundamental principle of use-after-free conditions where memory that has been deallocated is still referenced by subsequent operations. When Firefox processes images that require resizing, the imgLoader object manages the loading and dimension calculation process. However, during certain resize scenarios, the application fails to properly synchronize the lifecycle of this object, leading to situations where the memory previously allocated to the imgLoader becomes available for reuse while still being referenced. This creates a window of opportunity for attackers to manipulate the freed memory space, potentially overwriting critical function pointers or data structures with malicious payloads. The vulnerability is classified under CWE-416 as an improper free condition, which specifically addresses the incorrect handling of memory deallocation and subsequent access patterns.
The operational impact of CVE-2014-1531 extends beyond simple denial of service scenarios to encompass full remote code execution capabilities, making it a severe threat to user security. Attackers can craft malicious web pages that, when loaded in affected browsers, trigger the vulnerable code path through carefully constructed image elements and resize operations. The heap memory corruption resulting from this flaw can be exploited through various techniques including return-oriented programming and data injection methods that leverage the corrupted memory layout. This vulnerability affects not just Firefox but also Firefox ESR 24.x, Thunderbird 24.x, and SeaMonkey 2.26, indicating a widespread impact across Mozilla's product ecosystem. The exploitation chain typically involves loading a malicious webpage that contains specially crafted HTML elements and JavaScript code designed to force the browser into the vulnerable code path during image processing operations.
Mitigation strategies for CVE-2014-1531 focus primarily on immediate patching and application updates to address the root cause of the memory management flaw. Organizations should prioritize updating all affected Mozilla products to versions 29.0, 24.5, or later, respectively, as these releases contain the necessary fixes for the improper memory handling in the imgLoader object. Additionally, implementing browser security measures such as sandboxing, content security policies, and strict MIME type checking can provide additional defense layers against exploitation attempts. Network-level protections including web application firewalls and intrusion detection systems can help identify and block malicious content that attempts to trigger this vulnerability. Security teams should also consider implementing monitoring for unusual memory access patterns and heap corruption indicators that might signal exploitation attempts. The vulnerability demonstrates the importance of proper memory management in web browsers and highlights the need for comprehensive testing of edge cases in image processing and DOM manipulation scenarios. This flaw serves as a reminder of the critical nature of memory safety in modern web applications and the potential for seemingly benign operations like image resizing to become attack vectors when proper memory lifecycle management is not implemented.