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VulnerabilityPublished

CVE-2026-124903: Sandbox Escape Due to Use-after-free

Source GCVE Database

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Authoritative record:CVE-2026-124903· Critical 9.6

Not known to be exploited · CVSS 9.6 Critical.

Data as of 10 Nov 2026, 17:02 UTC

CVSS 3.1 base score
9.6Critical
How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none
CVSS scores by source
CISA-ADPCVSS 3.19.6
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 10 Nov 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq 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 10 Nov 2026.

What to do

AI-suggested

This vulnerability is fixed in Firefox 160, Firefox ESR 115.45, and Firefox ESR 153.7. Users and administrators should update to these versions or later to mitigate the risk. No additional mitigation steps are required beyond applying the official patches.

Description

CVE-2026-124903 is a critical use-after-free vulnerability in the IPC component of Firefox that allows sandbox escape. This flaw was addressed and fixed in Firefox 160 and Firefox ESR versions 115.45 and 153.7. The vulnerability has a high CVSS score of 9.6, indicating severe impact on confidentiality, integrity, and availability if exploited.

References

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