CVE-2026-4719
Published: 24 March 2026
Summary
CVE-2026-4719 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 34.8th 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-2026-4719 is a vulnerability involving incorrect boundary conditions in the Graphics: Text component of Mozilla Firefox and Thunderbird. It affects versions of Firefox prior to 149, Firefox ESR prior to 140.9, Thunderbird prior to 149, and Thunderbird prior to 140.9. The issue is classified under CWE-754 (Improper Check for Unusual or Exceptional Conditions) and CWE-119 (Buffer Errors), with a CVSS v3.1 base score of 7.5.
The vulnerability can be exploited by a remote, unauthenticated attacker with low complexity and no user interaction required. Successful exploitation results in a denial of service, specifically high-impact availability disruption (A:H), with no impact on confidentiality or integrity (C:N/I:N), over the network (AV:N) and without privilege requirements (PR:N).
Mozilla security advisories (MFSA 2026-20, 2026-22, 2026-23, and 2026-24) and the associated Bugzilla entry detail the patch releases that address the issue: Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9. Security practitioners should ensure affected products are updated to these versions or later to mitigate the vulnerability.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-14853
Vulnerability details
Incorrect boundary conditions in the Graphics: Text component. This vulnerability was fixed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
CVE enables remote exploitation of a buffer error in Firefox/Thunderbird graphics rendering, directly causing application crash and high-impact endpoint DoS with no other effects.
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Timely flaw remediation directly applies vendor patches (Firefox 149, ESR 140.9, Thunderbird 149/140.9) that correct the incorrect boundary conditions in the Graphics: Text component.
Vulnerability scanning identifies systems running affected versions of Firefox or Thunderbird prior to the patched releases.
Monitoring security advisories like Mozilla MFSA 2026-20/22/23/24 ensures awareness of this DoS vulnerability and triggers patching.
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