CVE-2026-0891
Last modified
CVE-2026-0891 is a high-severity vulnerability rated 8.1/10 on the CVSS scale. Memory safety bugs present in Firefox ESR 140.6, Thunderbird ESR 140.6, Firefox 146 and Thunderbird 146. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. EPSS estimates a 0.41% chance of exploitation in the next 30 days.
Description
Memory safety bugs present in Firefox ESR 140.6, Thunderbird ESR 140.6, Firefox 146 and Thunderbird 146. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability was fixed in Firefox 147, Firefox ESR 140.7, Thunderbird 147, and Thunderbird 140.7.
Metrics
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Weakness Enumeration
Affected Software
| Vendor | Product | Versions |
|---|---|---|
| Mozilla | Firefox | < 140.7.0 |
| Mozilla | Firefox | < 147.0 |
| Mozilla | Thunderbird | < 140.7.0 |
| Mozilla | Thunderbird | < 147.0 |
References
- https://www.mozilla.org/security/advisories/mfsa2026-01/Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2026-03/Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2026-04/Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2026-05/Vendor Advisory
Timeline
- Published
- Last Modified
- Status
- Modified
Frequently Asked Questions
What is CVE-2026-0891?
How severe is CVE-2026-0891?
How do I fix CVE-2026-0891?
How Strix Helps
- How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
- Autonomous PentestingAI agents that find and validate exploitable vulnerabilities like this one across your applications.
- PR ReviewsPentest every pull request so vulnerable code is caught before it ships to production.
- AI Penetration TestingHow AI-driven penetration testing continuously covers your attack surface.
Related CVEs from 2026
- CVE-2026-0885Use-after-free in the JavaScript: GC component. This vulnera…6.5
- CVE-2026-0886Incorrect boundary conditions in the Graphics component. Thi…5.3
- CVE-2026-0887Clickjacking issue, information disclosure in the PDF Viewer…4.3
- CVE-2026-0888Information disclosure in the XML component. This vulnerabil…5.3
- CVE-2026-0889Denial-of-service in the DOM: Service Workers component. Thi…7.5
- CVE-2026-0890Spoofing issue in the DOM: Copy & Paste and Drag & Drop comp…5.4
- CVE-2026-0892Memory safety bugs present in Firefox 146 and Thunderbird 14…9.8
- CVE-2026-0894The Content Blocks (Custom Post Widget) plugin for WordPress…6.4
- CVE-2026-0895The extension extends TYPO3’ FileSpool component, which was …5.2
- CVE-2026-0897Allocation of Resources Without Limits or Throttling in the …7.5
- CVE-2026-0898An arbitrary file-write vulnerability in Pega Browser Extens…9
- CVE-2026-0899Out of bounds memory access in V8 in Google Chrome prior to …8.8
Are you affected by CVE-2026-0891?
Run a free Strix scan to check your systems for this vulnerability.
Scan your code nowSource: NVD / NIST