CVE-2026-74990
Mozilla Firefox buffer overflow
- Published18 Aug 2026
Description
Internally found bugs present in Thunderbird ESR 140.13, Thunderbird ESR 153.0 and Thunderbird 153. Some of these bugs showed evidence of memory corruption or another security-relevant defect and we presume that with enough effort some of these could have been exploited. This vulnerability was fixed in Firefox 154, Firefox ESR 115.39, Firefox ESR 140.14, Firefox ESR 153.1, Thunderbird 154, Thunderbird 140.14, and Thunderbird 153.1.
CVSS 3.1 breakdown
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HAffected products
Remediation
- https://www.mozilla.org/security/advisories/mfsa2026-74/
- https://www.mozilla.org/security/advisories/mfsa2026-75/
- https://www.mozilla.org/security/advisories/mfsa2026-76/
- https://www.mozilla.org/security/advisories/mfsa2026-77/
- https://www.mozilla.org/security/advisories/mfsa2026-78/
- https://www.mozilla.org/security/advisories/mfsa2026-79/
References
- https://bugzilla.mozilla.org/buglist.cgi?bug_id=2045762%2C2052401%2C2058208
- https://bugzilla.mozilla.org/buglist.cgi?bug_id=2045774%2C2048490%2C2050864%2C2053159%2C2053260%2C2053261%2C2053582%2C2053599%2C2053607%2C2053608%2C2053853%2C2054626%2C2054627%2C2054635%2C2054677%2C2054740%2C2054832%2C2056792%2C2057098%2C2057100%2C2057101%2C2057103%2C2057117%2C2057118%2C2058048%2C2058049%2C2058622%2C2058623%2C2058665%2C2058666%2C2059121%2C2059164%2C2059188
- https://www.mozilla.org/security/advisories/mfsa2026-74/
- https://www.mozilla.org/security/advisories/mfsa2026-75/
- https://www.mozilla.org/security/advisories/mfsa2026-76/
- https://www.mozilla.org/security/advisories/mfsa2026-77/
- https://www.mozilla.org/security/advisories/mfsa2026-78/
- https://www.mozilla.org/security/advisories/mfsa2026-79/
- https://www.mozilla.org/security/advisories/mfsa2026-80/
Related CVEs
Recent high-severity vulnerabilities sharing a weakness type.
Frequently asked
Is CVE-2026-74990 being actively exploited?
CVE-2026-74990 is not in the CISA KEV catalog. Its EPSS exploit probability is 0.71%.
How severe is CVE-2026-74990?
CVE-2026-74990 has a CVSS 3.1 base score of 9.8, rated critical. EPSS estimates a 0.71% probability of exploitation.
Which products are affected by CVE-2026-74990?
Affected products include Mozilla Firefox, Mozilla Thunderbird.
How do I fix CVE-2026-74990?
Upgrade affected software to a fixed version, for example Mozilla Firefox 140.14.0, Mozilla Thunderbird 153.1.0 or later, then confirm no affected versions remain in your inventory.
How Secuno handles this
Secuno correlates vulnerabilities like CVE-2026-74990 against the real software inventory on every managed device, every day. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.
Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.