CVE-2026-117945 in Firefox
Summary
by MITRE • 10/27/2026
Incorrect boundary conditions in the XML component. This vulnerability was fixed in Firefox 159 and Firefox ESR 153.6.
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Analysis
by VulDB Data Team • 10/28/2026
The identified security issue stems from incorrect boundary condition handling within the Extensible Markup Language processing subsystem of Mozilla Firefox. In software engineering, boundary conditions refer to edge cases where input values are at the extreme ends of a range or set of acceptable inputs. When these boundaries are not rigorously validated and handled correctly by the parser, it can lead to memory corruption errors such as buffer overflows or out-of-bounds reads. This specific flaw indicates that the XML component failed to properly check array indices or string lengths during parsing operations, potentially allowing an attacker to manipulate data structures in a way that violates expected memory layout constraints.
From a technical perspective, this vulnerability aligns with CWE-193 Off-by-One Error and potentially CWE-787 Out-of-bounds Write if the boundary violation leads to writing beyond allocated memory regions. The XML parser is responsible for interpreting structured text data, which often originates from external sources such as web pages, extensions, or local files processed by browser components like SVG rendering engines or MathML processors. If an attacker can craft a maliciously formatted XML document that triggers these incorrect boundary checks during the parsing phase, they may induce undefined behavior within the application process. This could result in data corruption, crashes, or potentially arbitrary code execution depending on how the memory is subsequently utilized by other components of the browser architecture.
The operational impact of this vulnerability depends heavily on the attack vector and the specific context in which the vulnerable XML parsing occurs. If the flaw can be triggered through standard web content loading, it represents a significant risk to user confidentiality and integrity. An attacker could potentially exploit this condition to achieve remote code execution by carefully crafting payloads that leverage the memory corruption for control flow hijacking or information disclosure. Even if full exploitation is complex due to modern browser mitigations such as ASLR and DEP, the vulnerability still poses a denial-of-service threat through application crashes, disrupting user productivity and system stability. The existence of this flaw highlights the critical importance of robust input validation in core parsing libraries that handle untrusted data streams.
Mozilla addressed this security deficiency by releasing updates for Firefox version 159 and Firefox Extended Support Release (ESR) version 153.6. These patches likely involved rigorous code reviews, static analysis enhancements, and dynamic testing to identify the precise location of the boundary condition error within the XML component logic. The fix ensures that all input boundaries are correctly validated before processing, preventing out-of-bounds access attempts. Users running affected versions should upgrade immediately to mitigate potential exploitation risks associated with this memory safety issue.
In terms of industry standards and threat modeling, this vulnerability can be mapped to MITRE ATT&CK techniques related to initial execution or defense evasion if exploited for code injection, specifically falling under the broader category of software vulnerabilities that facilitate privilege escalation or remote access. Security practitioners should monitor future releases for additional patches addressing similar boundary condition flaws in other components like JSON parsers or HTML renderers. Implementing strict input sanitization and adopting memory-safe programming practices during development are essential strategies to prevent recurrence of such issues across web browser ecosystems.