CVE-2026-109705: Sandbox escape, site isolation issue due to incorrect boundary conditions, use-after-free in the
Source GCVE Database
Not known to be exploited · CVSS 9.6 Critical.
Data as of 27 Oct 2026, 17:11 UTC
- EPSS
- 0.3% chance of exploitation in 30 days – higher than 23% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/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
AI-suggested
This vulnerability has been fixed in Firefox 158 and Firefox ESR 153.5. Users and administrators should update to these versions or later to mitigate the risk. No additional mitigation steps are required beyond applying the official update.
Description
CVE-2026-109705 is a critical use-after-free vulnerability in the Networking component of Firefox that allows sandbox escape and site isolation bypass due to incorrect boundary conditions. This flaw was addressed and fixed in Firefox 158 and Firefox ESR 153.5.
References
- nvd.nist.gov/vuln/detail/CVE-2026-109705 (opens in a new tab)
- bugzilla.mozilla.org/show_bug.cgi?id=2040905 (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)
- mozilla.org/security/advisories/mfsa2026-119 (opens in a new tab)