Description
Sandbox escape due to use-after-free in the Networking component. This vulnerability was fixed in Firefox 158, Firefox ESR 153.5, Thunderbird 158, Thunderbird 153.5, and Firefox ESR 115.44.
Published: 2026-10-13
Score: 9.6 Critical
EPSS: < 1% Very Low
KEV: No
Impact: Sandbox escape
Action: Immediate Patch
AI Analysis

Impact

According to the updated description, a use‑after‑free bug in the Networking component of Firefox and Thunderbird allows a maliciously crafted web page or network request to escape the browser’s sandbox. This matches CWE‑416.

Affected Systems

Mozilla Firefox and Thunderbird are affected when running versions older than 158, and the extended support release versions 153.5, 115.44, and earlier. The patch was applied in Firefox 158, Firefox ESR 153.5, Firefox ESR 115.44, Thunderbird 158, and Thunderbird ESR 153.5, so any system using earlier releases is vulnerable.

Risk and Exploitability

The vulnerability has a CVSS score of 9.6, indicating critical severity. It has an EPSS score of < 1% and is not listed in the CISA KEV catalog at this time, but its nature – a sandbox escape via use‑after‑free – indicates a high‑risk impact if exploited. Attackers would need to supply malicious content that triggers the abnormal memory access; no additional configuration is required beyond normal browsing behavior.

Generated by OpenCVE AI on October 28, 2026 at 01:24 UTC.

Remediation

No solution or workaround provided in the CVE record.

OpenCVE Recommended Actions

  • Update Firefox or Thunderbird to the patched releases (Firefox 158 or ESR 153.5, Thunderbird 158 or ESR 153.5).
  • If an update cannot be applied immediately, monitor for security advisories and apply the update as soon as possible.
  • Apply network filtering or a firewall rule to block potentially untrusted traffic from unverified sources until the patch is available.

Generated by OpenCVE AI on October 28, 2026 at 01:24 UTC.

Tracking

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Advisories
Source ID Title
Debian DLA Debian DLA DLA-4836-1 firefox-esr security update
Debian DLA Debian DLA DLA-4863-1 thunderbird security update
Debian DSA Debian DSA DSA-6560-1 firefox-esr security update
History

Tue, 27 Oct 2026 15:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}

Tue, 27 Oct 2026 14:15:00 +0000

Type Values Removed Values Added
Description Sandbox escape due to use-after-free in the Networking component. This vulnerability was fixed in Firefox 158, Firefox ESR 153.5, Thunderbird 158, and Thunderbird 153.5. Sandbox escape due to use-after-free in the Networking component. This vulnerability was fixed in Firefox 158, Firefox ESR 153.5, Thunderbird 158, Thunderbird 153.5, and Firefox ESR 115.44.
References

Tue, 13 Oct 2026 18:30:00 +0000

Type Values Removed Values Added
Description Sandbox escape due to use-after-free in the Networking component. This vulnerability was fixed in Firefox 158 and Firefox ESR 153.5. Sandbox escape due to use-after-free in the Networking component. This vulnerability was fixed in Firefox 158, Firefox ESR 153.5, Thunderbird 158, and Thunderbird 153.5.
References

Tue, 13 Oct 2026 16:15:00 +0000

Type Values Removed Values Added
First Time appeared Mozilla
Mozilla firefox
Vendors & Products Mozilla
Mozilla firefox

Tue, 13 Oct 2026 15:30:00 +0000

Type Values Removed Values Added
Weaknesses CWE-416
Metrics cvssV3_1

{'score': 9.6, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H'}

Tue, 13 Oct 2026 13:00:00 +0000

Type Values Removed Values Added
Description Sandbox escape due to use-after-free in the Networking component. This vulnerability was fixed in Firefox 158 and Firefox ESR 153.5.
Title Sandbox escape due to use-after-free in the Networking component
References

Subscriptions

Mozilla Firefox
cve-icon MITRE

Status: PUBLISHED

Assigner: mozilla

Published:

Updated: 2026-10-27T14:05:57.668Z

Reserved: 2026-10-13T00:29:16.501Z

Link: CVE-2026-109707

cve-icon Vulnrichment

Updated: 2026-10-13T14:14:02.531Z

cve-icon NVD

Status : Deferred

Published: 2026-10-13T13:17:20.803

Modified: 2026-10-27T14:16:32.697

Link: CVE-2026-109707

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-10-28T01:30:14Z

Weaknesses