Raw vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:HSummary
CVE-2026-4686 is a high-severity Improper Check for Unusual or Exceptional Conditions (CWE-754) vulnerability in Mozilla Firefox. Its CVSS base score is 7.5 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Privilege Escalation (T1068); ranked in the top 49% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified map to SA-11 (Developer Testing and Evaluation) and SI-10 (Information Input Validation) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2026-4686 is a vulnerability involving incorrect boundary conditions in the Graphics: Canvas2D component of Mozilla Firefox and Thunderbird. It affects versions of Firefox prior to 149, Firefox ESR prior to 115.34 and 140.9, and Thunderbird prior to 149 and 140.9. The issue, classified under CWE-754 (Improper Check for Unusual or Exceptional Conditions), carries a CVSS v3.1 base score of 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H) and was publicly disclosed on March 24, 2026.
Attackers can exploit this vulnerability remotely over the network with low complexity, requiring no privileges, authentication, or user interaction. Successful exploitation results in high-impact denial of service, such as application crashes, without affecting confidentiality or integrity.
Mozilla's security advisories (MFSA 2026-20 through 2026-23) and the associated Bugzilla entry (bug 2016351) confirm the vulnerability was addressed in the listed fixed releases. Security practitioners should prioritize updating affected Firefox and Thunderbird installations to mitigate the risk of remote crashes.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-14796
Vulnerability Data
Incorrect boundary conditions in the Graphics: Canvas2D component. This vulnerability was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
—
—
- 7 hardening rules · 2 OS baselines
—
Mitigating Controls (NIST 800-53 r5) AI
Developer testing and evaluation explicitly exercises unusual conditions to find missing or incorrect checks.
Input validation directly requires checking for unexpected or malformed conditions before they propagate.
Requiring documented secure-development standards and tools can mandate bounds-checked coding practices that avoid the weakness.
Security engineering principles include structured handling of edge cases and exceptions during design.
Memory-protection mechanisms limit the exploitability and blast radius of a successful out-of-bounds write.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Secure development practices directly require proper checks and handling for exceptional conditions throughout the SDLC.
Runtime monitoring of software and environments can detect adverse events triggered by unhandled exceptional conditions.
Vulnerability scanning and recording can discover out-of-bounds write flaws so they can be remediated.
Patching or replacing vulnerable software directly eliminates known instances of this coding weakness.
Generating logs of exceptions and errors enables detection of improper handling of unusual conditions.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Security testing in development and acceptance verifies handling of error and exceptional conditions.
Logging can record unhandled exceptions but does not prevent the weakness itself.
Monitoring may detect symptoms of unhandled conditions but does not eliminate the root weakness.
Secure development life cycle mandates exception handling and input validation that directly prevent missing checks for unusual conditions.
Application security requirements explicitly call for handling of exceptional conditions and error paths.
Secure system architecture and engineering principles require robust error and exception handling mechanisms.
Hardening callouts derived
Configuration rules from DISA STIG baselines that bear on weaknesses of the type cited by this CVE. Each rule is shown with the relationship its mapping actually records, against the CWE it was authored against. Derived via CVE→CWE over `controls_xwalks` (authoritative rows only; rows rated `none` are excluded).
Oracle Linux 8 (2 rules)
- V-248574 YUM must be configured to prevent the installation of patches, service packs, device drivers, or OL 8 system components that have not been digitally signed using a certificate that is recognized and approved by the organization. prevents CWE-754
- V-248575 OL 8 must prevent the installation of software, patches, service packs, device drivers, or operating system components of local packages without verification they have been digitally signed using a certificate that is issued by a Certificate Authority (CA) that is recognized and approved by the organization. prevents CWE-754
Oracle Linux 9 (1 rule)
- V-271452 OL 9 must use a Linux Security Module configured to enforce limits on system services. prevents CWE-754