CVE-2017-7786 in Firefox
Summary
by MITRE
A buffer overflow can occur when the image renderer attempts to paint non-displayable SVG elements. This results in a potentially exploitable crash. This vulnerability affects Thunderbird < 52.3, Firefox ESR < 52.3, and Firefox < 55.
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Analysis
by VulDB Data Team • 01/09/2021
The vulnerability identified as CVE-2017-7786 represents a critical buffer overflow condition within the SVG rendering subsystem of Mozilla Firefox and Thunderbird applications. This flaw manifests when the image renderer encounters SVG elements that cannot be properly displayed, creating a scenario where memory allocation becomes compromised. The vulnerability stems from insufficient input validation and bounds checking during the processing of malformed or non-standard SVG content, making it particularly dangerous in web browsing environments where users may encounter arbitrary SVG files from untrusted sources.
The technical implementation of this vulnerability places the affected applications at risk of arbitrary code execution through memory corruption. When the SVG renderer attempts to process non-displayable elements, the buffer overflow occurs in the rendering pipeline where insufficient bounds checking allows data to be written beyond allocated memory buffers. This condition creates potential for stack corruption or heap corruption depending on the specific implementation details, which can be exploited by malicious actors to inject and execute arbitrary code within the context of the affected application. The vulnerability specifically impacts versions prior to 52.3 for Firefox ESR and Thunderbird, and 55 for standard Firefox releases, indicating a window of exposure that required immediate patching.
The operational impact of CVE-2017-7786 extends beyond simple application crashes to encompass full system compromise potential. Attackers can leverage this vulnerability through crafted SVG files delivered via web pages, email attachments, or other vectors where SVG content might be rendered. The exploitation typically involves creating malicious SVG elements that trigger the buffer overflow condition during rendering, potentially leading to remote code execution on vulnerable systems. This makes the vulnerability particularly dangerous in enterprise environments where users may encounter untrusted content through various attack vectors, including phishing campaigns, malicious websites, or compromised web services.
Security professionals should consider this vulnerability in the context of the CWE-121 buffer overflow weakness classification, which specifically addresses the condition where data is written beyond the boundaries of a fixed-length buffer. The ATT&CK framework categorizes this as a code injection technique, specifically involving memory corruption vulnerabilities that enable privilege escalation and system compromise. Mitigation strategies should include immediate patch deployment for all affected versions, implementation of content security policies to restrict SVG rendering, and network-level controls to filter potentially malicious SVG content. Additionally, organizations should consider implementing sandboxing mechanisms and regular vulnerability assessments to prevent exploitation of similar rendering vulnerabilities in other components of their software ecosystem.