CVE-2026-74987
Internally found bugs fixed in Firefox ESR 140.14, Firefox ESR 153.1 and Firefox 154
- State
- Published
- Severity
- 9.8 Critical
- Published
- Aug 18, 2026
- Updated
- Oct 28, 2026
- Reserved
- Aug 17, 2026
Description
Internally found bugs present in Firefox ESR 140.13, Firefox ESR 153.0 and Firefox 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 140.14, Firefox ESR 153.1, Thunderbird 154, Thunderbird 140.14, and Thunderbird 153.1.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 3.1 | 9.8 Critical | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H | CISA-ADP |
Weaknesses
- CWE-119 Improper Restriction of Operations within the Bounds of a Memory Buffer
Affected Products
| Product | Versions |
|---|---|
FirefoxMozilla |
|
ThunderbirdMozilla |
|
References
- Moderate Severity internally found bugs fixed in Firefox ESR 140.14, Firefox ESR 153.1 and Firefox 154
- High Severity internally found bugs fixed in Firefox ESR 140.14, Firefox ESR 153.1 and Firefox 154
- Low Severity internally found bugs fixed in Firefox ESR 140.14, Firefox ESR 153.1 and Firefox 154
- https://www.mozilla.org/security/advisories/mfsa2026-74/
- 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/
Every record here comes from the CVE Program’s CVE List. © 1999–2026 The MITRE Corporation. CVE is a registered trademark of The MITRE Corporation. The records are reproduced under the CVE Program terms of use.