CVE-2026-109761: Use-after-free in the JavaScript · WebAssembly component
Affects mozjs52Source GCVE Database
Not known to be exploited · CVSS 5.4 Medium.
Data as of 29 Oct 2026, 00:28 UTC
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 13 Oct 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: 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 26 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
This vulnerability is fixed in Firefox 158 and Thunderbird 158. Users and administrators should update to these or later versions to remediate the issue. No additional mitigation steps are required as the fix is official and available.
Description
A use-after-free vulnerability exists in the JavaScript WebAssembly component of Mozilla's mozjs52 engine. This flaw was addressed and fixed in Firefox 158 and Thunderbird 158. The vulnerability has a medium severity rating with a CVSS score of 5.4, indicating limited confidentiality and integrity impact without availability impact. There are no known exploits in the wild. The affected versions include specific mozjs52 builds used in various Ubuntu and other distributions.
References
- ubuntu.com/security/CVE-2026-109761 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2026-109761 (opens in a new tab)
- mozilla.org/en-US/security/advisories/mfsa2026-106/ (opens in a new tab)
- bugzilla.mozilla.org/show_bug.cgi?id=2071764 (opens in a new tab)
- mozilla.org/security/advisories/mfsa2026-106/ (opens in a new tab)
- mozilla.org/security/advisories/mfsa2026-109/ (opens in a new tab)