CVE-2017-5380 in Firefox
Summary
by MITRE
A potential use-after-free found through fuzzing during DOM manipulation of SVG content. This vulnerability affects Thunderbird < 45.7, Firefox ESR < 45.7, and Firefox < 51.
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Analysis
by VulDB Data Team • 11/26/2025
This vulnerability represents a critical use-after-free condition that emerged during fuzzing operations targeting DOM manipulation of Scalable Vector Graphics content. The flaw occurs when the browser processes SVG elements within web pages, specifically during dynamic modifications to the Document Object Model. The vulnerability stems from improper memory management where freed memory locations are still being accessed or referenced by subsequent operations, creating a potential exploitation vector for malicious actors. The issue affects multiple Mozilla products including Thunderbird and various Firefox versions, indicating a widespread impact across the browser ecosystem. The vulnerability classification aligns with CWE-416, which specifically addresses use-after-free conditions in memory management. This type of vulnerability is particularly dangerous because it can lead to arbitrary code execution when attackers manipulate the freed memory to redirect program flow or inject malicious payloads. The exploitation requires careful crafting of SVG content that triggers the specific memory management flaw during DOM operations.
The technical implementation of this vulnerability involves the interaction between SVG rendering engine and DOM manipulation routines within the browser's JavaScript engine. When processing SVG content, the browser allocates memory for SVG elements and their associated properties, but fails to properly manage the lifecycle of these memory allocations during dynamic modifications. During fuzzing operations, specific sequences of DOM manipulation commands combined with SVG content trigger a scenario where memory is freed but subsequent operations attempt to reference the same memory locations. This creates a race condition where the freed memory can be reallocated for other purposes, and if an attacker can control the content that gets allocated to this memory, they can potentially execute arbitrary code. The vulnerability demonstrates the complexity of modern browser security where interactions between different subsystems create unexpected attack surfaces.
The operational impact of this vulnerability extends beyond simple browser crashes or instability, presenting significant security risks for end users. Attackers could potentially exploit this vulnerability through malicious websites that embed crafted SVG content, leading to complete system compromise without user interaction. The affected versions represent a substantial portion of deployed browser installations, particularly the Firefox ESR releases that organizations often rely on for stability and security. The vulnerability affects both desktop and mobile browser implementations, with the potential for cross-platform exploitation. Security researchers have noted that such use-after-free conditions are particularly challenging to mitigate because they often require deep architectural changes to memory management systems rather than simple patching. The vulnerability also impacts email clients like Thunderbird, which process rich content including SVG elements, expanding the attack surface to include email-based exploitation vectors.
Mitigation strategies for this vulnerability encompass multiple layers of defense including immediate patch deployment, browser hardening measures, and content filtering approaches. Organizations should prioritize updating affected browser versions to the patched releases, specifically Firefox 51 and Thunderbird 45.7 or later. The Mozilla security team recommends enabling sandboxing features and restricting SVG content processing in untrusted environments. Additional protective measures include implementing content security policies that limit SVG processing, using web application firewalls to filter malicious content, and deploying browser security extensions that monitor for suspicious DOM manipulation patterns. Security professionals should also consider implementing monitoring systems that detect unusual memory access patterns or browser instability that might indicate exploitation attempts. The vulnerability highlights the importance of continuous security testing including fuzzing operations and the need for robust memory management practices in complex software systems. Organizations should also conduct regular vulnerability assessments focusing on DOM manipulation and SVG processing components to identify similar issues before they can be exploited in the wild.