CVE-2026-4729: Mozilla Firefox · Buffer Overflow
Affects Mozilla FirefoxSource CVE Database V5
Not known to be exploited · CVSS 9.8 Critical.
Data as of 29 Oct 2026, 19:04 UTC
Contested
Critical score, yet low EPSS after six months- EPSS
- 0.3% chance of exploitation in 30 days – higher than 27% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HExploitation evidence
Disclosed: evidence found.
CVE published 24 Mar 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 29 Oct 2026.
What to do
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| Mozilla Firefox | Affected
| Fixed in– |
AI-suggested
Official fixes addressing these vulnerabilities are available in Mozilla Firefox 149 and Thunderbird 149. Users and administrators should update to these versions or later to remediate the issues. Since this is not a cloud service, local patching is required. No additional mitigation actions are indicated by the vendor advisory beyond applying the official updates.
Description
Memory safety bugs present in Firefox 148 and Thunderbird 148. 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 149 and Thunderbird 149.
References
- bugzilla.mozilla.org/buglist.cgi?bug_id=1944033%2C1997282%2C2009213%2C2011412%2C2021925%2C2022034 (opens in a new tab)
- mozilla.org/security/advisories/mfsa2026-20/ (opens in a new tab)
- mozilla.org/security/advisories/mfsa2026-23/ (opens in a new tab)
- access.redhat.com/security/cve/CVE-2026-4729 (opens in a new tab)
- bugzilla.redhat.com/show_bug.cgi?id=2450745 (opens in a new tab)
- security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-4729.json (opens in a new tab)