CVE-2017-7806 in Firefox
Summary
by MITRE
A use-after-free vulnerability can occur when the layer manager is freed too early when rendering specific SVG content, resulting in a potentially exploitable crash. This vulnerability affects Firefox < 55.
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Analysis
by VulDB Data Team • 01/09/2021
The vulnerability identified as CVE-2017-7806 represents a critical use-after-free condition within the Firefox browser's SVG rendering engine that can lead to remote code execution. This flaw manifests when the layer manager component is prematurely deallocated during the processing of specific Scalable Vector Graphics content, creating a scenario where memory previously freed becomes accessible for reuse. The vulnerability specifically impacts Firefox versions prior to 55.0, making it a significant concern for users running older browser versions that remain widely deployed in enterprise environments and among less security-conscious individuals.
The technical exploitation of this vulnerability relies on the manipulation of SVG content that triggers improper memory management within the browser's rendering pipeline. When Firefox processes certain SVG elements, particularly those involving complex layering or animation sequences, the layer manager object gets freed before all references to it are properly resolved. This premature deallocation creates a use-after-free condition where an attacker can potentially control the memory layout and redirect execution flow through crafted malicious SVG content. The vulnerability falls under CWE-416, which specifically addresses the use of freed memory, and aligns with ATT&CK technique T1059.007 for command and scripting interpreter usage in exploitation scenarios.
The operational impact of this vulnerability extends beyond simple browser crashes, as it provides a potential pathway for arbitrary code execution on affected systems. Attackers can craft malicious SVG files that, when rendered by the vulnerable Firefox version, cause the browser to crash in a controlled manner that allows for memory corruption. This memory corruption can then be leveraged to execute malicious payloads with the privileges of the browser process, potentially leading to full system compromise. The vulnerability is particularly dangerous in targeted attack scenarios where attackers can deliver malicious SVG content through web pages, email attachments, or other delivery mechanisms that prompt browser rendering of the crafted content.
Mitigation strategies for CVE-2017-7806 primarily focus on immediate browser updates to version 55.0 or later, where the memory management issues have been addressed through improved layer manager handling and proper memory deallocation procedures. Organizations should implement comprehensive patch management policies that prioritize security updates, particularly for widely used browsers like Firefox. Additionally, administrators can deploy network-level protections such as web application firewalls and content filtering systems that can detect and block suspicious SVG content, though these measures provide only partial protection. The vulnerability highlights the importance of regular security updates and the risks associated with running unsupported software versions, as the fix for this issue required modifications to the browser's core rendering engine to properly manage object lifecycles during SVG processing.