Memory safety bugs present in Firefox ESR 115.34.0, Firefox ESR 140.9.0, Thunderbird ESR 140.9.0, Firefox 149.0.1 and Thunderbird 149.0.1. 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 149.0.2, Firefox ESR 115.34.1, Firefox ESR 140.9.1, Thunderbird 149.0.2, and Thunderbird 140.9.1.

Project Subscriptions

Vendors Products
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Firefox Esr Subscribe
Thunderbird Subscribe
Advisories
Source ID Title
Debian DLA Debian DLA DLA-4526-1 firefox-esr security update
Debian DLA Debian DLA DLA-4534-1 thunderbird security update
Debian DSA Debian DSA DSA-6202-1 firefox-esr security update
Debian DSA Debian DSA DSA-6211-1 thunderbird security update
Fixes

Solution

No solution given by the vendor.


Workaround

No workaround given by the vendor.

References
Link Providers
https://access.redhat.com/errata/RHSA-2026:11805 cve-icon
https://access.redhat.com/errata/RHSA-2026:11813 cve-icon
https://access.redhat.com/errata/RHSA-2026:12264 cve-icon
https://access.redhat.com/errata/RHSA-2026:13342 cve-icon
https://access.redhat.com/errata/RHSA-2026:13412 cve-icon
https://access.redhat.com/errata/RHSA-2026:13533 cve-icon
https://access.redhat.com/errata/RHSA-2026:13582 cve-icon
https://access.redhat.com/errata/RHSA-2026:13583 cve-icon
https://access.redhat.com/errata/RHSA-2026:13596 cve-icon
https://access.redhat.com/errata/RHSA-2026:13600 cve-icon
https://access.redhat.com/errata/RHSA-2026:13665 cve-icon
https://access.redhat.com/errata/RHSA-2026:13682 cve-icon
https://access.redhat.com/errata/RHSA-2026:13683 cve-icon
https://access.redhat.com/errata/RHSA-2026:13922 cve-icon
https://access.redhat.com/errata/RHSA-2026:13977 cve-icon
https://access.redhat.com/errata/RHSA-2026:14223 cve-icon
https://access.redhat.com/errata/RHSA-2026:14303 cve-icon
https://access.redhat.com/errata/RHSA-2026:15889 cve-icon
https://access.redhat.com/errata/RHSA-2026:7671 cve-icon
https://access.redhat.com/errata/RHSA-2026:7672 cve-icon
https://access.redhat.com/errata/RHSA-2026:8052 cve-icon
https://access.redhat.com/errata/RHSA-2026:8459 cve-icon
https://access.redhat.com/errata/RHSA-2026:9345 cve-icon
https://access.redhat.com/errata/RHSA-2026:9638 cve-icon
https://access.redhat.com/security/cve/CVE-2026-5731 cve-icon
https://bugzilla.mozilla.org/buglist.cgi?bug_id=2021894%2C2022225%2C2022252%2C2022294%2C2023007%2C2023130%2C2023191%2C2023364%2C2023829%2C2024074%2C2024417%2C2024433%2C2024436%2C2024437%2C2024453%2C2024461%2C2024462%2C2024472%2C2024474%2C2024477%2C2025364%2C2025401%2C2025402%2C2025472%2C2026287%2C2026299%2C2026305%2C2026426 cve-icon cve-icon
https://bugzilla.redhat.com/show_bug.cgi?id=2455901 cve-icon
https://nvd.nist.gov/vuln/detail/CVE-2026-5731 cve-icon
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-5731.json cve-icon
https://www.cve.org/CVERecord?id=CVE-2026-5731 cve-icon
https://www.mozilla.org/security/advisories/mfsa2026-25/ cve-icon cve-icon
https://www.mozilla.org/security/advisories/mfsa2026-26/ cve-icon cve-icon
https://www.mozilla.org/security/advisories/mfsa2026-27/ cve-icon cve-icon
https://www.mozilla.org/security/advisories/mfsa2026-27/#CVE-2026-5731 cve-icon
https://www.mozilla.org/security/advisories/mfsa2026-28/ cve-icon cve-icon
https://www.mozilla.org/security/advisories/mfsa2026-29/ cve-icon cve-icon
https://www.mozilla.org/security/advisories/mfsa2026-29/#CVE-2026-5731 cve-icon
History

Thu, 28 May 2026 10:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

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

ssvc

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


Thu, 16 Apr 2026 19:00:00 +0000

Type Values Removed Values Added
CPEs cpe:2.3:a:mozilla:firefox:115.34.0:*:*:*:esr:*:*:*
cpe:2.3:a:mozilla:firefox:140.9.0:*:*:*:esr:*:*:*
cpe:2.3:a:mozilla:firefox:149.0.1:*:*:*:-:*:*:*
cpe:2.3:a:mozilla:thunderbird:140.9.0:*:*:*:esr:*:*:*
cpe:2.3:a:mozilla:thunderbird:149.0.1:*:*:*:-:*:*:*

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

Type Values Removed Values Added
Description Memory safety bugs present in Firefox ESR 115.34.0, Firefox ESR 140.9.0, Thunderbird ESR 140.9.0, Firefox 149.0.1 and Thunderbird 149.0.1. 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 affects Firefox < 149.0.2, Firefox ESR < 115.34.1, Firefox ESR < 140.9.1, Thunderbird < 149.0.2, and Thunderbird < 140.9.1. Memory safety bugs present in Firefox ESR 115.34.0, Firefox ESR 140.9.0, Thunderbird ESR 140.9.0, Firefox 149.0.1 and Thunderbird 149.0.1. 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 149.0.2, Firefox ESR 115.34.1, Firefox ESR 140.9.1, Thunderbird 149.0.2, and Thunderbird 140.9.1.

Wed, 08 Apr 2026 20:15:00 +0000

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

Wed, 08 Apr 2026 12:30:00 +0000


Tue, 07 Apr 2026 20:45:00 +0000

Type Values Removed Values Added
Description Memory safety bugs present in Firefox ESR 115.34.0, Firefox ESR 140.9.0, Thunderbird ESR 140.9.0, Firefox 149.0.1 and Thunderbird 149.0.1. 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 affects Firefox < 149.0.2, Firefox ESR < 115.34.1, and Firefox ESR < 140.9.1. Memory safety bugs present in Firefox ESR 115.34.0, Firefox ESR 140.9.0, Thunderbird ESR 140.9.0, Firefox 149.0.1 and Thunderbird 149.0.1. 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 affects Firefox < 149.0.2, Firefox ESR < 115.34.1, Firefox ESR < 140.9.1, Thunderbird < 149.0.2, and Thunderbird < 140.9.1.
References

Tue, 07 Apr 2026 15:15:00 +0000

Type Values Removed Values Added
Description Memory safety bugs present in Firefox ESR 115.34.0, Firefox ESR 140.9.0, Thunderbird ESR 140.9.0, Firefox 149.0.1 and Thunderbird 149.0.1. 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 affects Firefox < 149.0.2, Firefox ESR < 115.34.1, and Firefox ESR < 140.9.1.
Title Memory safety bugs fixed in Firefox ESR 115.34.1, Firefox ESR 140.9.1, Thunderbird ESR 140.9.1, Firefox 149.0.2 and Thunderbird 149.0.2
Weaknesses CWE-119
References
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'}


Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: mozilla

Published:

Updated: 2026-07-15T00:42:22.695Z

Reserved: 2026-04-07T12:43:11.413Z

Link: CVE-2026-5731

cve-icon Vulnrichment

Updated: 2026-07-15T00:42:22.695Z

cve-icon NVD

Status : Modified

Published: 2026-04-07T13:16:47.347

Modified: 2026-07-15T01:16:43.827

Link: CVE-2026-5731

cve-icon Redhat

Severity : Important

Publid Date: 2026-04-07T12:43:11Z

Links: CVE-2026-5731 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2026-04-14T16:41:04Z

Weaknesses