CVE-2026-109778: Mozjs52 · Privilege escalation in the WebExtensions component
Affects mozjs52Source GCVE Database
Not known to be exploited · CVSS 8.8 High.
Data as of 28 Oct 2026, 23:44 UTC
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 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
Apply the official fixes by upgrading to Firefox 158, Firefox ESR 153.5, Thunderbird 158, or Thunderbird 153.5 as appropriate. These versions contain the patches that remediate this vulnerability. No additional mitigation steps are indicated by the vendor advisory.
Description
CVE-2026-109778 is a high-severity privilege escalation vulnerability in the WebExtensions component of mozjs52. It allows an attacker to escalate privileges, potentially leading to full compromise of the affected application. This vulnerability was fixed in Firefox 158, Firefox ESR 153.5, Thunderbird 158, and Thunderbird 153.5.
References
- ubuntu.com/security/CVE-2026-109778 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2026-109778 (opens in a new tab)
- mozilla.org/en-US/security/advisories/mfsa2026-106/ (opens in a new tab)
- mozilla.org/en-US/security/advisories/mfsa2026-108/ (opens in a new tab)
- mozilla.org/en-US/security/advisories/mfsa2026-109/ (opens in a new tab)
- bugzilla.mozilla.org/show_bug.cgi?id=2070547 (opens in a new tab)
- mozilla.org/security/advisories/mfsa2026-106/ (opens in a new tab)
- mozilla.org/security/advisories/mfsa2026-108/ (opens in a new tab)
- mozilla.org/security/advisories/mfsa2026-109/ (opens in a new tab)
- mozilla.org/security/advisories/mfsa2026-110/ (opens in a new tab)