CVE-2026-92021: Mozjs52 · Use-after-free in the JavaScript Engine: JIT component
Affects mozjs52Source GCVE Database
Not known to be exploited · CVSS 8.8 High · fixed in 140.16 : patch mozjs52 soon.
Data as of 30 Oct 2026, 20:25 UTC
- EPSS
- 0.2% chance of exploitation in 30 days – higher than 20% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 140.16
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:HExploitation evidence
Disclosed: evidence found.
CVE published 15 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 30 Oct 2026.
What to do
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Ubuntu 24.04 LTSmozjs102pkg:deb/ubuntu/mozjs102?arch=source&distro=nobleOther threats | Affected
| Fixed in– |
Ubuntu 24.04 LTSmozjs115pkg:deb/ubuntu/mozjs115?arch=source&distro=nobleOther threats | Affected
| Fixed in– |
Ubuntu 22.04 LTSmozjs102pkg:deb/ubuntu/mozjs102?arch=source&distro=jammyOther threats | Affected
| Fixed in– |
Ubuntu 22.04 LTSmozjs78pkg:deb/ubuntu/mozjs78?arch=source&distro=jammyOther threats | Affected
| Fixed in– |
Ubuntu 22.04 LTSmozjs91pkg:deb/ubuntu/mozjs91?arch=source&distro=jammyOther threats | Affected
| Fixed in– |
Ubuntu 22.04 LTSthunderbirdpkg:deb/ubuntu/thunderbird?arch=source&distro=jammyOther threats | Affected
| Fixed in– |
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
An official fix is available and has been released in Firefox ESR 140.16 and Thunderbird 140.16. Users and administrators should update affected products to these versions or later to remediate this vulnerability. The vendor advisory does not indicate any additional mitigation steps or that the issue is already mitigated without patching.
Description
CVE-2026-92021 is a use-after-free vulnerability in the JavaScript Engine's JIT component of mozjs52. This vulnerability was fixed in Firefox ESR 140.16 and Thunderbird 140.16. It has a high impact rating with a CVSS score of 8.8, indicating potential for significant confidentiality, integrity, and availability impact. The vulnerability affects multiple specific versions of mozjs52 as listed, including various Ubuntu package versions. No known exploits in the wild have been reported. The vendor advisory confirms the availability of an official fix.
References
- nvd.nist.gov/vuln/detail/CVE-2026-92021 (opens in a new tab)
- bugzilla.mozilla.org/show_bug.cgi?id=2067208 (opens in a new tab)
- mozilla.org/security/advisories/mfsa2026-92 (opens in a new tab)
- mozilla.org/security/advisories/mfsa2026-95 (opens in a new tab)
- ubuntu.com/security/CVE-2026-92021 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2026-92021 (opens in a new tab)