CVE-2026-117886 in Firefox
Summary
by MITRE • 10/27/2026
Incorrect boundary conditions in the Graphics: Text component. This vulnerability was fixed in Firefox 159, Firefox ESR 115.44, and Firefox ESR 153.6.
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Analysis
by VulDB Data Team • 10/27/2026
The identified security issue resides within the text rendering subsystem of Mozilla Firefox, specifically affecting the Graphics Text component responsible for processing font metrics and layout boundaries. This vulnerability stems from incorrect boundary condition handling during the calculation of glyph positions or character spacing. In complex typographic scenarios involving mixed scripts, variable fonts, or specific Unicode sequences, the engine may fail to properly validate input dimensions against expected limits. Such logic errors can lead to memory corruption states where the application writes data beyond allocated buffer boundaries or reads from invalid memory locations. The root cause is typically a lack of rigorous validation checks on calculated offsets before they are applied to rendering pipelines, allowing malformed text inputs to trigger out-of-bounds access patterns within the graphics stack.
From an operational perspective, this flaw poses significant risks related to stability and potential code execution. While many boundary condition vulnerabilities in browser engines result primarily in denial of service through crashes or hangs due to segmentation faults, sophisticated exploitation could potentially lead to arbitrary code execution if the memory corruption allows for controlled overwrites of critical data structures such as function pointers or object headers. Attackers could craft malicious web pages containing specially designed text elements that exploit these boundary miscalculations when rendered in a victim's browser session. The impact is particularly severe because it affects core rendering functionality, meaning any webpage utilizing rich text formatting could serve as an attack vector without requiring user interaction beyond visiting the site or having content auto-rendered via scripts.
This vulnerability aligns with Common Weakness Enumeration category CWE-190, which describes integer overflow or wraparound errors that lead to buffer overflows, and CWE-787, concerning out-of-bounds writes in memory management contexts. In terms of adversary tactics, it relates to ATT&CK technique T1203, Exploitation for Client Execution, where attackers leverage software vulnerabilities in client applications like web browsers to gain initial access or execute malicious payloads on the target system. The flaw highlights the complexity inherent in modern browser engines that must handle diverse and often unpredictable input data from the open web while maintaining strict memory safety guarantees.
Mitigation strategies primarily involve applying the vendor-provided patches released for Firefox 159, Firefox Extended Support Release version 115.44, and Firefox ESR version 153.6. These updates contain corrected logic within the text component to properly enforce boundary checks during glyph layout calculations. Organizations relying on enterprise deployments should prioritize updating their browser fleets to these patched versions immediately to eliminate the attack surface associated with this specific rendering flaw. Additionally, users can employ content security policies and sandboxing mechanisms provided by modern browsers to limit the potential impact of any successful exploitation attempt, although patching remains the definitive remediation step for this class of vulnerability.