CVE-2026-4707
Published: 24 March 2026
Summary
CVE-2026-4707 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 Application or System Exploitation (T1499.004); ranked at the 43.3th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified are NIST 800-53 SI-2 (Flaw Remediation) and RA-5 (Vulnerability Monitoring and Scanning).
Deeper analysis
CVE-2026-4707 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 is classified under CWE-754 (Improper Check for Unusual or Exceptional Conditions) and carries a CVSS v3.1 base score of 7.5.
An unauthenticated attacker can exploit this vulnerability remotely over the network with low complexity and no user interaction required. Successful exploitation leads to a denial-of-service condition with high availability impact, as indicated by the CVSS vector (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H), potentially causing browser or application crashes.
Mozilla security advisories (MFSA 2026-20 through 2026-23) and the associated Bugzilla entry detail the fix applied in the listed versions. Security practitioners should prioritize updating affected Firefox and Thunderbird installations to mitigate the risk.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-14829
Vulnerability details
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 TechniquesAI
Why these techniques?
CVE describes remote unauthenticated exploitation of a boundary condition flaw in Firefox/Thunderbird Canvas2D that directly produces application crashes (high availability impact, no other effects), matching T1499.004 Application or System Exploitation for Endpoint Denial of Service.
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Directly requires timely remediation of flaws like CVE-2026-4707 through patching Firefox and Thunderbird to fixed versions, preventing remote DoS exploitation.
Provides vulnerability scanning to identify systems with vulnerable Firefox or Thunderbird versions affected by CVE-2026-4707's boundary condition flaw.
Ensures monitoring of security advisories such as Mozilla MFSA 2026-20 to promptly learn of and apply fixes for CVE-2026-4707.
Hardening callouts derived
Configuration rules from DISA STIG baselines that reduce the attack surface for weaknesses of the type cited by this CVE. Derived transitively via CVE→CWE→STIG over `controls_xwalks` (authoritative rows only).
Oracle Linux 8 (3 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. via CWE-754
- V-248573 The OL 8 file integrity tool must notify the system administrator (SA) when changes to the baseline configuration or anomalies in the operation of any security functions are discovered within an organizationally defined frequency. via 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. via CWE-754
Oracle Linux 9 (1 rule)
- V-271452 OL 9 must use a Linux Security Module configured to enforce limits on system services. via CWE-754