Description
Use-after-free in the Widget component. This vulnerability was fixed in Firefox ESR 153.4, Thunderbird 157, Thunderbird 140.17, Thunderbird 153.4, Firefox 157, Firefox ESR 115.42, and Firefox ESR 140.17.
Published: 2026-09-29
Score: 8.8 High
EPSS: < 1% Very Low
KEV: No
Impact: Use‑after‑free potentially enabling remote code execution via the widget component
Action: Patch
AI Analysis

Impact

The flaw is a use‑after‑free in the Widget component, which can be triggered by malicious content and may allow arbitrary code execution or a crash. The vulnerability has been addressed in several newer releases, including Firefox 157, Firefox ESR 153.4, Firefox ESR 115.42, Firefox ESR 140.17, Thunderbird 157, Thunderbird 153.4, and Thunderbird 140.17.

Affected Systems

Mozilla Firefox and Mozilla Thunderbird are affected, with the patch included in Firefox ESR 153.4, Firefox 157, Firefox ESR 115.42, and Firefox ESR 140.17, and in Thunderbird 157, Thunderbird 153.4, and Thunderbird 140.17. Versions older than those enumerated remain vulnerable.

Risk and Exploitability

The CVSS score of 8.8 is available, and the EPSS score is less than 1%. The vulnerability is not listed in CISA KEV. The likely attack vector is through malicious web content that triggers the widget, enabling a remote attacker to exploit the use‑after‑free for code execution or denial of service.

Generated by OpenCVE AI on October 1, 2026 at 03:21 UTC.

Remediation

No solution or workaround provided in the CVE record.

OpenCVE Recommended Actions

  • Upgrade to Firefox 157 or a newer release, or to ESR 153.4, ESR 115.42, or ESR 140.17 which contain the patch.
  • If an update cannot be applied, disable the widget component via about:config or remove the related plugin to prevent exploitation.
  • Monitor browser behavior and logs for anomalies that could indicate exploitation attempts.

Generated by OpenCVE AI on October 1, 2026 at 03:21 UTC.

Tracking

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Advisories
Source ID Title
Debian DLA Debian DLA DLA-4810-1 thunderbird security update
Debian DLA Debian DLA DLA-4814-1 firefox-esr security update
Debian DSA Debian DSA DSA-6533-1 firefox-esr security update
Debian DSA Debian DSA DSA-6536-1 thunderbird security update
History

Tue, 13 Oct 2026 21:15:00 +0000

Type Values Removed Values Added
First Time appeared Mozilla thunderbird
CPEs cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:*
Vendors & Products Mozilla thunderbird

Wed, 30 Sep 2026 17:45:00 +0000

Type Values Removed Values Added
Description Use-after-free in the Widget component. This vulnerability was fixed in Firefox ESR 153.4, Thunderbird 157, Firefox 157, Firefox ESR 115.42, and Firefox ESR 140.17. Use-after-free in the Widget component. This vulnerability was fixed in Firefox ESR 153.4, Thunderbird 157, Thunderbird 140.17, Thunderbird 153.4, Firefox 157, Firefox ESR 115.42, and Firefox ESR 140.17.
References

Wed, 30 Sep 2026 17:30:00 +0000

Type Values Removed Values Added
Description Use-after-free in the Widget component. This vulnerability was fixed in Firefox ESR 153.4, Firefox 157, Firefox ESR 115.42, and Firefox ESR 140.17. Use-after-free in the Widget component. This vulnerability was fixed in Firefox ESR 153.4, Thunderbird 157, Firefox 157, Firefox ESR 115.42, and Firefox ESR 140.17.
References

Wed, 30 Sep 2026 05:15:00 +0000

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

Tue, 29 Sep 2026 16:30:00 +0000

Type Values Removed Values Added
Weaknesses CWE-416
Metrics cvssV3_1

{'score': 8.8, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H'}

ssvc

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

Tue, 29 Sep 2026 13:15:00 +0000

Type Values Removed Values Added
Description Use-after-free in the Widget component. This vulnerability was fixed in Firefox ESR 153.4, Firefox 157, Firefox ESR 115.42, and Firefox ESR 140.17.
Title Use-after-free in the Widget component
References

Subscriptions

Mozilla Firefox Thunderbird
cve-icon MITRE

Status: PUBLISHED

Assigner: mozilla

Published:

Updated: 2026-09-30T17:19:58.761Z

Reserved: 2026-09-26T19:15:14.718Z

Link: CVE-2026-100757

cve-icon Vulnrichment

Updated: 2026-09-29T15:10:49.554Z

cve-icon NVD

Status : Analyzed

Published: 2026-09-29T13:17:40.047

Modified: 2026-10-13T21:03:29.033

Link: CVE-2026-100757

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-10-01T03:30:17Z

Weaknesses