CVE-2026-117993 in Firefox
Summary
by MITRE • 10/27/2026
Integer overflow in the Graphics: Text component. This vulnerability was fixed in Firefox 159 and Firefox ESR 153.6.
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Analysis
by VulDB Data Team • 10/27/2026
The identified vulnerability resides within the text rendering subsystem of the Gecko layout engine, specifically affecting how integer values are processed during graphical operations involving typography. Integer overflow vulnerabilities occur when an arithmetic operation results in a value that exceeds the maximum capacity of the data type used to store it. In this context, the flaw likely involves calculations related to font metrics, glyph positioning, or buffer sizing for text strings where unsigned integers wrap around upon exceeding their limit. This mathematical error can lead to incorrect memory allocation sizes being computed by the browser engine. When a smaller size is allocated than what is actually required for subsequent operations, it creates a scenario ripe for heap-based buffer overflows or out-of-bounds writes when the system attempts to write data into the undersized buffer.
From an operational perspective, this vulnerability allows for potential memory corruption within the Firefox process space. An attacker could craft a malicious webpage containing specially designed text elements with specific font properties and Unicode characters that trigger the integer overflow during rendering. By exploiting the resulting memory mismanagement, it is possible to achieve arbitrary code execution on the victim's machine if combined with other exploitation techniques such as heap spraying or use-after-free conditions. Even without full remote code execution, this flaw can lead to denial of service through application crashes due to segmentation faults caused by invalid memory access patterns generated during text layout calculations.
This issue aligns closely with Common Weakness Enumeration category CWE-190, which defines integer overflow or wraparound. The exploitation vector typically falls under the ATT&CK technique T1203, specifically referencing exploit code for client-side vulnerabilities like browsers and web applications. It also relates to CWE-787, out-of-bounds write, as a direct consequence of the miscalculated buffer size derived from the integer overflow. Security researchers classify this type of flaw within the broader category of memory safety issues that are prevalent in C++ based codebases where manual memory management is required without sufficient bounds checking during arithmetic operations involving user-controlled or dynamically computed values.
The resolution for this vulnerability was implemented in Firefox version 159 and Firefox Extended Support Release version 153.6. The fix likely involves adding explicit checks to ensure that calculated sizes do not exceed valid limits before memory allocation occurs, or utilizing safe integer types that prevent wraparound behavior during critical rendering calculations. Users are strongly advised to update their browsers immediately to mitigate the risk of exploitation. Since this vulnerability affects core graphical components used in almost every web page interaction, delaying updates leaves systems exposed to sophisticated attacks targeting text processing pipelines. Enterprise administrators should ensure that automated patching policies include these specific version numbers to maintain a secure browsing environment across all endpoints.