CVE-2026-100758: Mozilla Firefox · Improper Access Control
Affects Mozilla FirefoxSource CVE Database V5
Not known to be exploited · CVSS 9.6 Critical · fixed in 153.4 : patch Mozilla Firefox as a priority.
Data as of 13 Nov 2026, 23:53 UTC
- EPSS
- 0.3% chance of exploitation in 30 days – higher than 23% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 153.4
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:HExploitation evidence
Disclosed: evidence found.
CVE published 29 Sep 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 13 Nov 2026.
What to do
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| Mozilla Firefox | Affected
| Fixed in
|
AI-suggested
Official patches are available and should be applied immediately. Users should upgrade to Firefox ESR 153.4 or later, Firefox 157 or later, Thunderbird 140.17 or later, Thunderbird 153.4 or later, or Thunderbird 157 or later. No additional mitigations are indicated by the vendor advisory.
Description
CVE-2026-100758 is a critical sandbox escape vulnerability in the DOM navigation component of Mozilla Firefox and Thunderbird. It allows an attacker to bypass sandbox restrictions, potentially leading to full compromise of confidentiality, integrity, and availability. The issue has been fixed in Firefox ESR 153.4, Firefox 157, Firefox ESR 115.42, Firefox ESR 140.17, Thunderbird 140.17, Thunderbird 153.4, and Thunderbird 157.
References
- bugzilla.mozilla.org/show_bug.cgi?id=2049792 (opens in a new tab)
- mozilla.org/security/advisories/mfsa2026-100/ (opens in a new tab)
- mozilla.org/security/advisories/mfsa2026-97/ (opens in a new tab)
- mozilla.org/security/advisories/mfsa2026-98/ (opens in a new tab)
- mozilla.org/security/advisories/mfsa2026-99/ (opens in a new tab)
- mozilla.org/security/advisories/mfsa2026-101/ (opens in a new tab)
- mozilla.org/security/advisories/mfsa2026-102/ (opens in a new tab)
- mozilla.org/security/advisories/mfsa2026-103/ (opens in a new tab)