CVE-2026-12321: Mozilla Firefox · CWE-670
Affects Mozilla FirefoxSource CVE Database V5
Not known to be exploited · CVSS 5.4 Medium · patch available : update Mozilla Firefox when convenient.
Data as of 30 Oct 2026, 06:59 UTC
- EPSS
- 0.1% chance of exploitation in 30 days – higher than 5% 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:R/S:U/C:L/I:L/A:NExploitation evidence
Disclosed: evidence found.
CVE published 16 Jun 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
A fix for this vulnerability is available in Mozilla Firefox version 152. Users and administrators should update affected Firefox installations to version 152 or later to remediate this issue. The vendor advisory confirms the official fix. No additional mitigation actions are required beyond applying the update.
Description
CVE-2026-12321 is a low-impact vulnerability involving JIT miscompilation in the JavaScript WebAssembly component of Mozilla Firefox. This issue was fixed in Firefox version 152. The vulnerability is part of a broader set of security fixes released in Firefox 152 and Thunderbird 152 addressing multiple memory safety bugs, sandbox escapes, and other issues. The CVSS score for this specific vulnerability is 5.4 (medium severity), but the vendor rates its impact as low. No known exploits are reported in the wild. Users running Firefox versions prior to 152 are affected.