Description
Internally found bugs present in Thunderbird 154, Thunderbird ESR 153.1 and Thunderbird ESR 140.14. Some of these bugs showed evidence of memory corruption or another security-relevant defect and we presume that with enough effort some of these could have been exploited. This vulnerability was fixed in Firefox 155, Firefox ESR 115.40, Firefox ESR 140.15, Firefox ESR 153.2, Thunderbird 155, Thunderbird 140.15, and Thunderbird 153.2.
Published: 2026-09-01
Score: 7.5 High
EPSS: < 1% Very Low
KEV: No
Impact: Potential memory corruption leading to arbitrary code execution
Action: Immediate Patch
AI Analysis

Impact

Internally discovered bugs in Thunderbird 154 and the corresponding ESR releases (ESR 153.1 and ESR 140.14) exhibited memory corruption or other security‑relevant defects. If successfully exploited, these flaws could allow an attacker to execute arbitrary code on the affected systems, potentially compromising confidentiality, integrity, or availability.

Affected Systems

The vulnerable builds are Thunderbird 154, ESR 153.1, and ESR 140.14, along with the matching Firefox releases. The issue is resolved in Thunderbird 155, ESR 153.2, and ESR 140.15, and in Firefox 155, ESR 115.40, ESR 140.15, and ESR 153.2. Updating to any of these releases removes the vulnerability.

Risk and Exploitability

The CVSS score of 7.5 indicates a high severity vulnerability. The EPSS score is less than 1%, indicating a very low probability of exploitation in the wild. The likely attack vector is local user interaction with untrusted data, such as a crafted email or web content, to trigger memory corruption. If an attacker succeeds, arbitrary code execution and full system compromise are possible. The vulnerability is not listed in CISA KEV.

Generated by OpenCVE AI on September 11, 2026 at 06:37 UTC.

Remediation

No vendor fix or workaround currently provided.

OpenCVE Recommended Actions

  • Upgrade Thunderbird to version 155 or the corresponding ESR releases (153.2 or 140.15) to obtain the patch
  • Upgrade Firefox to version 155 or the corresponding ESR releases (115.40, 140.15, or 153.2)
  • Apply the security patches outlined in Mozilla’s MFSA2026‑82 to MFSA2026‑88 advisories
  • Monitor for signs of exploitation or related incidents following the update

Generated by OpenCVE AI on September 11, 2026 at 06:37 UTC.

Tracking

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Advisories
Source ID Title
Debian DLA Debian DLA DLA-4770-1 firefox-esr security update
Debian DLA Debian DLA DLA-4775-1 thunderbird security update
Debian DSA Debian DSA DSA-6481-1 firefox-esr security update
Debian DSA Debian DSA DSA-6483-1 thunderbird security update
History

Fri, 11 Sep 2026 00:15:00 +0000

Type Values Removed Values Added
Weaknesses CWE-825
References
Metrics threat_severity

None

 threat_severity

Important

Thu, 03 Sep 2026 13:00:00 +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

Tue, 01 Sep 2026 22:00:00 +0000

Type Values Removed Values Added
Description Internally found bugs present in Firefox 154, Firefox ESR 153.1, Firefox ESR 140.14 and Firefox ESR 115.39. Some of these bugs showed evidence of memory corruption or another security-relevant defect and we presume that with enough effort some of these could have been exploited. This vulnerability was fixed in Firefox 155, Firefox ESR 115.40, Firefox ESR 140.15, and Firefox ESR 153.2. Internally found bugs present in Thunderbird 154, Thunderbird ESR 153.1 and Thunderbird ESR 140.14. Some of these bugs showed evidence of memory corruption or another security-relevant defect and we presume that with enough effort some of these could have been exploited. This vulnerability was fixed in Firefox 155, Firefox ESR 115.40, Firefox ESR 140.15, Firefox ESR 153.2, Thunderbird 155, Thunderbird 140.15, and Thunderbird 153.2.
Title Internally found bugs fixed in Firefox 155, Firefox ESR 153.2, Firefox ESR 140.15 and Firefox ESR 115.40 Internally found bugs fixed in Thunderbird 155, Thunderbird ESR 153.2 and Thunderbird ESR 140.15
References
Metrics ssvc

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

Tue, 01 Sep 2026 15:30:00 +0000

Type Values Removed Values Added
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H'}

Tue, 01 Sep 2026 14:15:00 +0000

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

Tue, 01 Sep 2026 14:00:00 +0000

Type Values Removed Values Added
Weaknesses CWE-119

Tue, 01 Sep 2026 12:45:00 +0000

Type Values Removed Values Added
Description Internally found bugs present in Firefox 154, Firefox ESR 153.1, Firefox ESR 140.14 and Firefox ESR 115.39. Some of these bugs showed evidence of memory corruption or another security-relevant defect and we presume that with enough effort some of these could have been exploited. This vulnerability was fixed in Firefox 155, Firefox ESR 115.40, Firefox ESR 140.15, and Firefox ESR 153.2.
Title Internally found bugs fixed in Firefox 155, Firefox ESR 153.2, Firefox ESR 140.15 and Firefox ESR 115.40
References

Subscriptions

Mozilla Firefox Thunderbird
cve-icon MITRE

Status: PUBLISHED

Assigner: mozilla

Published:

Updated: 2026-09-02T03:55:49.167Z

Reserved: 2026-09-01T07:26:02.411Z

Link: CVE-2026-84145

cve-icon Vulnrichment

Updated: 2026-09-01T15:04:39.691Z

cve-icon NVD

Status : Analyzed

Published: 2026-09-01T13:20:08.673

Modified: 2026-09-03T12:49:55.293

Link: CVE-2026-84145

cve-icon Redhat

Severity : Important

Publid Date: 2026-09-01T12:18:43Z

Links: CVE-2026-84145 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2026-09-11T06:45:06Z

Weaknesses
  • CWE-119

    Improper Restriction of Operations within the Bounds of a Memory Buffer

  • CWE-825

    Expired Pointer Dereference