CVE-2017-5472 in Firefox
Summary
by MITRE
A use-after-free vulnerability with the frameloader during tree reconstruction while regenerating CSS layout when attempting to use a node in the tree that no longer exists. This results in a potentially exploitable crash. This vulnerability affects Firefox < 54, Firefox ESR < 52.2, and Thunderbird < 52.2.
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Analysis
by VulDB Data Team • 11/26/2025
The vulnerability described in CVE-2017-5472 represents a critical use-after-free condition within the Firefox browser's frameloader component that occurs during tree reconstruction and CSS layout regeneration processes. This flaw exists in the way the browser handles DOM node references when the underlying memory structure has already been freed but references to it persist. The vulnerability specifically manifests when the browser attempts to access a node in the document tree that has been deallocated during the layout process, creating a scenario where memory that has been freed can still be accessed and potentially manipulated by malicious actors.
The technical implementation of this vulnerability involves the interaction between the browser's rendering engine and its memory management systems. During CSS layout regeneration, the frameloader component maintains references to DOM nodes that may be removed or relocated during the tree reconstruction process. When a node is freed from memory but the system continues to reference it during layout calculations, the use-after-free condition occurs. This type of vulnerability falls under CWE-416 which specifically addresses the use of freed memory conditions in software systems. The flaw demonstrates how improper memory management during complex rendering operations can create exploitable conditions that allow attackers to execute arbitrary code.
The operational impact of this vulnerability is severe as it can be exploited to achieve remote code execution on affected systems. Attackers can craft malicious web content that triggers the specific sequence of events leading to the use-after-free condition, potentially allowing them to execute arbitrary code with the privileges of the browser process. This makes the vulnerability particularly dangerous in web browsing environments where users may encounter malicious content without proper security awareness. The affected versions include Firefox versions prior to 54, Firefox ESR versions prior to 52.2, and Thunderbird versions prior to 52.2, representing a significant portion of the user base that would be vulnerable to exploitation. The vulnerability aligns with ATT&CK technique T1203 which describes the exploitation of memory corruption vulnerabilities for code execution.
Mitigation strategies for this vulnerability require immediate patching of affected software versions to ensure proper memory management during tree reconstruction and CSS layout operations. Organizations should prioritize updating their Firefox and Thunderbird installations to the patched versions that address the memory management issues in the frameloader component. Additionally, implementing browser hardening measures such as address space layout randomization and heap corruption detection can provide additional layers of protection. Security monitoring should focus on detecting attempts to exploit memory corruption vulnerabilities through unusual browser behavior or access patterns. The fix implemented by Mozilla likely involved strengthening the memory management routines in the frameloader to properly track node references during layout operations and ensure that freed memory cannot be accessed or manipulated by the rendering engine.