CVE-2026-8956: Mozilla Firefox · Integer Overflow
Affects Mozilla FirefoxSource CVE Database V5
Not known to be exploited · CVSS 9.8 Critical · patch available : patch Mozilla Firefox as a priority.
Data as of 30 Oct 2026, 11:52 UTC
- EPSS
- 0.6% chance of exploitation in 30 days – higher than 48% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available
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 19 May 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 30 Oct 2026.
What to do
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| Mozilla Firefox | Affected
| Fixed in
|
AI-suggested
Mozilla has officially fixed this vulnerability in Firefox 151 and Firefox ESR 140.11. Users should update their Firefox installations to these versions or later to remediate this issue. Since the vulnerability is patched, no additional mitigation steps are required beyond applying the official update.
Description
Integer overflow in the Networking: JAR component. This vulnerability was fixed in Firefox 151, Firefox ESR 140.11, Thunderbird 151, and Thunderbird 140.11.
References
- bugzilla.mozilla.org/show_bug.cgi?id=2032427 (opens in a new tab)
- mozilla.org/security/advisories/mfsa2026-46/ (opens in a new tab)
- mozilla.org/security/advisories/mfsa2026-48/ (opens in a new tab)
- mozilla.org/security/advisories/mfsa2026-50/ (opens in a new tab)
- mozilla.org/security/advisories/mfsa2026-51/ (opens in a new tab)