Description
Memory safety bugs present in Firefox ESR 115.35, Firefox ESR 140.10 and Firefox 150. 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 151, Firefox ESR 115.36, Firefox ESR 140.11, Thunderbird 151, and Thunderbird 140.11.
Published: 2026-05-19
Score: 8.8 High
EPSS: < 1% Very Low
KEV: No
Impact: n/a
Action: n/a
AI Analysis

Impact

Memory safety bugs were present in Mozilla Firefox ESR 115.35, Firefox ESR 140.10, and Firefox 150. The defects could corrupt process memory and, with sufficient effort, allow an attacker to execute arbitrary code. The same fixes also address Firefox 151, Firefox ESR 115.36, and Firefox ESR 140.11, and were applied to Mozilla Thunderbird in versions 151 and 140.11. These defects correspond to buffer overflow (CWE-119) and out-of-bounds write (CWE-787) vulnerabilities.

Affected Systems

Affected products include Mozilla Firefox ESR 115.35, Firefox ESR 140.10, and Firefox 150. The vulnerability was fixed by upgrading to Firefox 151, Firefox ESR 115.36, or Firefox ESR 140.11. The same fixes were applied to Mozilla Thunderbird, with Thunderbird 151 and Thunderbird 140.11 addressing the same memory safety issues. Earlier Thunderbird releases were not explicitly listed but are presumed to be affected by the same underlying flaw.

Risk and Exploitability

The EPSS score is reported as less than 1%, indicating a low but non‑zero exploitation probability, and the weakness is not listed in the CISA KEV catalog. The CVSS score of 8.8 indicates high severity. The attack vector is not specified; it is inferred that the exploitation could arise from processing untrusted content, whether locally or remotely. Due to the lack of publicly reported exploitation, the risk assessment relies solely on the described vulnerability features.

Generated by OpenCVE AI on May 26, 2026 at 19:48 UTC.

Remediation

No vendor fix or workaround currently provided.

OpenCVE Recommended Actions

  • Update Mozilla Thunderbird to version 151 or newer, or to the newer supported version 140.11, to apply the memory safety fixes.
  • Apply the same update to Mozilla Firefox, installing version 151, Firefox ESR 115.36, or Firefox ESR 140.11.
  • Restart all affected Thunderbird and Firefox instances after the update to ensure the new binaries are running.
  • If an upgrade cannot be performed immediately, limit exposure by disabling add‑ons or features that load untrusted external content until a patched version is available.

Generated by OpenCVE AI on May 26, 2026 at 19:48 UTC.

Tracking

Sign in to view the affected projects.

Advisories
Source ID Title
Debian DLA Debian DLA DLA-4592-1 firefox-esr security update
Debian DLA Debian DLA DLA-4594-1 thunderbird security update
Debian DSA Debian DSA DSA-6283-1 firefox-esr security update
Debian DSA Debian DSA DSA-6288-1 thunderbird security update
History

Tue, 26 May 2026 18:00:00 +0000

Type Values Removed Values Added
Description Memory safety bugs present in Thunderbird 140.10 and Thunderbird 150. 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 151, Firefox ESR 115.36, Firefox ESR 140.11, Thunderbird 151, and Thunderbird 140.11. Memory safety bugs present in Firefox ESR 115.35, Firefox ESR 140.10 and Firefox 150. 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 151, Firefox ESR 115.36, Firefox ESR 140.11, Thunderbird 151, and Thunderbird 140.11.
Title Memory safety bugs fixed in Thunderbird 140.11 and Thunderbird 151 Memory safety bugs fixed in Firefox ESR 115.36, Firefox ESR 140.11 and Firefox 151

Fri, 22 May 2026 00:15:00 +0000

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

None

 threat_severity

Important

Thu, 21 May 2026 09:15:00 +0000

Type Values Removed Values Added
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'}

 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'}

Wed, 20 May 2026 14:45:00 +0000

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

Tue, 19 May 2026 18:15:00 +0000

Type Values Removed Values Added
Weaknesses CWE-120
CWE-122

Tue, 19 May 2026 17:45:00 +0000

Type Values Removed Values Added
Description Memory safety bugs present in Firefox ESR 115.35, Firefox ESR 140.10 and Firefox 150. 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 151, Firefox ESR 115.36, and Firefox ESR 140.11. Memory safety bugs present in Thunderbird 140.10 and Thunderbird 150. 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 151, Firefox ESR 115.36, Firefox ESR 140.11, Thunderbird 151, and Thunderbird 140.11.
Title Memory safety bugs fixed in Firefox ESR 115.36, Firefox ESR 140.11 and Firefox 151 Memory safety bugs fixed in Thunderbird 140.11 and Thunderbird 151
References

Tue, 19 May 2026 16:30:00 +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, 19 May 2026 15:45:00 +0000

Type Values Removed Values Added
Weaknesses CWE-120
CWE-122

Tue, 19 May 2026 15:15:00 +0000

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

Tue, 19 May 2026 13:45:00 +0000

Type Values Removed Values Added
Description Memory safety bugs present in Firefox ESR 115.35, Firefox ESR 140.10 and Firefox 150. 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 151, Firefox ESR 115.36, and Firefox ESR 140.11.
Title Memory safety bugs fixed in Firefox ESR 115.36, Firefox ESR 140.11 and Firefox 151
References

Subscriptions

Mozilla Firefox Thunderbird
cve-icon MITRE

Status: PUBLISHED

Assigner: mozilla

Published:

Updated: 2026-05-26T17:47:38.144Z

Reserved: 2026-05-19T12:30:23.949Z

Link: CVE-2026-8975

cve-icon Vulnrichment

Updated: 2026-05-19T15:17:55.326Z

cve-icon NVD

Status : Modified

Published: 2026-05-19T14:16:54.090

Modified: 2026-05-26T18:16:57.840

Link: CVE-2026-8975

cve-icon Redhat

Severity : Important

Publid Date: 2026-05-19T12:30:24Z

Links: CVE-2026-8975 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2026-05-26T20:00:15Z

Weaknesses
  • CWE-119

    Improper Restriction of Operations within the Bounds of a Memory Buffer

  • CWE-787

    Out-of-bounds Write