Description
Memory safety bugs present in Firefox ESR 140.12 and Firefox 152. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability was fixed in Firefox 153, Firefox ESR 140.13, Thunderbird 153, and Thunderbird 140.13.
Published: 2026-07-21
Score: 9.8 Critical
EPSS: < 1% Very Low
KEV: No
Impact: n/a
Action: n/a
AI Analysis

Impact

Memory safety bugs were reported in Firefox ESR 140.12 and Firefox 152. The bugs caused memory corruption and, with enough effort, could potentially be exploited to run arbitrary code on an affected system. The issue has been addressed in Firefox 153, Firefox ESR 140.13, Thunderbird 153, and Thunderbird 140.13.

Affected Systems

The vulnerable releases are Mozilla Firefox ESR 140.12, Firefox 152, and the corresponding Thunderbird products that share the same codebase. The flaw was fixed in Firefox 153, Firefox ESR 140.13, Thunderbird 153, and Thunderbird ESR 140.13. Systems that have not applied these updates remain at risk.

Risk and Exploitability

The CVSS score of 9.8 classifies this vulnerability as critical, while the EPSS score of less than 1% indicates a low probability of exploitation in the near term. The vulnerability is not listed in CISA’s KEV catalog. The attack vector is not explicitly documented; it is inferred that an attacker would need to trigger the memory corruption, likely by supplying crafted input or a malicious file to the browser or email client, but precise exploitation conditions are not disclosed.

Generated by OpenCVE AI on August 3, 2026 at 00:39 UTC.

Remediation

No vendor fix or workaround currently provided.

OpenCVE Recommended Actions

  • Update all affected installations to Firefox ESR 140.13 or any newer release, or to Firefox 153.
  • Update all affected Thunderbird installations to Thunderbird ESR 140.13 or any newer release, or to Thunderbird 153.
  • If updating immediately is not possible, isolate the affected systems from external networks and monitor for signs of exploitation attempts such as anomalous processes or unexpected network traffic.

Generated by OpenCVE AI on August 3, 2026 at 00:39 UTC.

Tracking

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Advisories
Source ID Title
Debian DLA Debian DLA DLA-4695-1 firefox-esr security update
Debian DLA Debian DLA DLA-4727-1 thunderbird security update
Debian DSA Debian DSA DSA-6394-1 firefox-esr security update
Debian DSA Debian DSA DSA-6418-1 thunderbird security update
History

Fri, 24 Jul 2026 00:30:00 +0000

Type Values Removed Values Added
Weaknesses CWE-787
References
Metrics threat_severity

None

 threat_severity

Important

Thu, 23 Jul 2026 15:45:00 +0000

Type Values Removed Values Added
Description Memory safety bugs present in Thunderbird ESR 140.12 and Thunderbird 152. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability was fixed in Firefox 153, Firefox ESR 140.13, Thunderbird 153, and Thunderbird 140.13. Memory safety bugs present in Firefox ESR 140.12 and Firefox 152. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability was fixed in Firefox 153, Firefox ESR 140.13, Thunderbird 153, and Thunderbird 140.13.
Title Memory safety bugs fixed in Thunderbird ESR 140.13 and Thunderbird 153 Memory safety bugs fixed in Firefox ESR 140.13 and Firefox 153

Wed, 22 Jul 2026 20:00:00 +0000

Type Values Removed Values Added
Description Memory safety bugs present in Firefox ESR 140.12 and Firefox 152. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability was fixed in Firefox 153 and Firefox ESR 140.13. Memory safety bugs present in Thunderbird ESR 140.12 and Thunderbird 152. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability was fixed in Firefox 153, Firefox ESR 140.13, Thunderbird 153, and Thunderbird 140.13.
Title Memory safety bugs fixed in Firefox ESR 140.13 and Firefox 153 Memory safety bugs fixed in Thunderbird ESR 140.13 and Thunderbird 153
References

Tue, 21 Jul 2026 21:45:00 +0000

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

Tue, 21 Jul 2026 20:30:00 +0000

Type Values Removed Values Added
Weaknesses CWE-119
Metrics cvssV3_1

{'score': 9.8, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H'}

ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}

Tue, 21 Jul 2026 12:45:00 +0000

Type Values Removed Values Added
Description Memory safety bugs present in Firefox ESR 140.12 and Firefox 152. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability was fixed in Firefox 153 and Firefox ESR 140.13.
Title Memory safety bugs fixed in Firefox ESR 140.13 and Firefox 153
References

Subscriptions

Mozilla Firefox
cve-icon MITRE

Status: PUBLISHED

Assigner: mozilla

Published:

Updated: 2026-07-24T03:55:34.396Z

Reserved: 2026-07-20T21:57:54.488Z

Link: CVE-2026-16412

cve-icon Vulnrichment

Updated: 2026-07-21T19:12:26.163Z

cve-icon NVD

Status : Modified

Published: 2026-07-21T13:17:16.630

Modified: 2026-07-24T05:16:40.790

Link: CVE-2026-16412

cve-icon Redhat

Severity : Important

Publid Date: 2026-07-21T12:38:23Z

Links: CVE-2026-16412 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2026-08-03T00:45:03Z

Weaknesses
  • CWE-119

    Improper Restriction of Operations within the Bounds of a Memory Buffer

  • CWE-787

    Out-of-bounds Write