Description
Sandbox escape due to incorrect boundary conditions, integer overflow in the XPCOM component. This vulnerability was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.
Published: 2026-03-24
Score: 9.6 Critical
EPSS: < 1% Very Low
KEV: No
Impact: Remote Code Execution
Action: Immediate Patch
AI Analysis

Impact

A flaw in the XPCOM component causes an integer overflow through improper boundary checks, allowing a sandbox escape that could let an attacker execute arbitrary code with the privileges of the affected application. The weakness is classed under CWE-120, CWE-190, and CWE-754.

Affected Systems

Mozilla Firefox and Thunderbird are affected. Versions prior to Firefox 149, Firefox ESR 115.34 and ESR 140.9, Thunderbird 149 and Thunderbird 140.9 contain the flaw; the stated releases include the fix.

Risk and Exploitability

The CVSS score of 9.6 marks the vulnerability as critical, and the EPSS score indicates a low probability of exploitation. The CVE description does not specify an attack vector, so it is inferred that an attacker would need to supply crafted data to a sandboxed process, but the precise method is not described. The flaw is not yet listed in the CISA KEV catalog.

Generated by OpenCVE AI on April 13, 2026 at 16:54 UTC.

Remediation

No vendor fix or workaround currently provided.

OpenCVE Recommended Actions

  • Upgrade Firefox to version 149 or newer, or to ESR 115.34 or newer, and upgrade Thunderbird to version 149 or newer, or to ESR 140.9 or newer.
  • Until a patched version can be installed, limit exposure by disabling or restricting the affected XPCOM component when possible, and monitor Mozilla advisories for updates.

Generated by OpenCVE AI on April 13, 2026 at 16:54 UTC.

Tracking

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Advisories
Source ID Title
Debian DLA Debian DLA DLA-4510-1 firefox-esr security update
Debian DLA Debian DLA DLA-4511-1 thunderbird security update
Debian DSA Debian DSA DSA-6178-1 firefox-esr security update
Debian DSA Debian DSA DSA-6179-1 thunderbird security update
History

Mon, 13 Apr 2026 14:30:00 +0000

Type Values Removed Values Added
Description Sandbox escape due to incorrect boundary conditions, integer overflow in the XPCOM component. This vulnerability affects Firefox < 149, Firefox ESR < 115.34, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9. Sandbox escape due to incorrect boundary conditions, integer overflow in the XPCOM component. This vulnerability was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.

Thu, 26 Mar 2026 00:15:00 +0000

Type Values Removed Values Added
References
Metrics threat_severity

None

 threat_severity

Important

Wed, 25 Mar 2026 14:15:00 +0000

Type Values Removed Values Added
Weaknesses CWE-120
Metrics cvssV3_1

{'score': 8.6, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H'}

 ssvc

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

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'}

Wed, 25 Mar 2026 12:00:00 +0000

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

Tue, 24 Mar 2026 20:30:00 +0000

Type Values Removed Values Added
Description Sandbox escape due to incorrect boundary conditions, integer overflow in the XPCOM component. This vulnerability affects Firefox < 149, Firefox ESR < 115.34, and Firefox ESR < 140.9. Sandbox escape due to incorrect boundary conditions, integer overflow in the XPCOM component. This vulnerability affects Firefox < 149, Firefox ESR < 115.34, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9.
References

Tue, 24 Mar 2026 19:30:00 +0000

Type Values Removed Values Added
First Time appeared Mozilla
Mozilla firefox
Weaknesses CWE-190
CWE-754
CPEs cpe:2.3:a:mozilla:firefox:*:*:*:*:-:*:*:*
cpe:2.3:a:mozilla:firefox:*:*:*:*:esr:*:*:*
Vendors & Products Mozilla
Mozilla firefox
Metrics cvssV3_1

{'score': 8.6, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H'}

Tue, 24 Mar 2026 12:45:00 +0000

Type Values Removed Values Added
Description Sandbox escape due to incorrect boundary conditions, integer overflow in the XPCOM component. This vulnerability affects Firefox < 149, Firefox ESR < 115.34, and Firefox ESR < 140.9.
Title Sandbox escape due to incorrect boundary conditions, integer overflow in the XPCOM component
References

Subscriptions

Mozilla Firefox Firefox Esr
cve-icon MITRE

Status: PUBLISHED

Assigner: mozilla

Published:

Updated: 2026-04-13T13:48:40.559Z

Reserved: 2026-03-23T23:21:42.156Z

Link: CVE-2026-4690

cve-icon Vulnrichment

Updated: 2026-03-25T13:15:54.195Z

cve-icon NVD

Status : Modified

Published: 2026-03-24T13:16:04.837

Modified: 2026-04-13T15:17:37.640

Link: CVE-2026-4690

cve-icon Redhat

Severity : Important

Publid Date: 2026-03-24T12:30:23Z

Links: CVE-2026-4690 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2026-04-14T16:43:40Z

Weaknesses