CVE-2026-5731

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.
References
Link Resource
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 Broken Link
https://www.mozilla.org/security/advisories/mfsa2026-25/ Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-26/ Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-27/ Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-28/ Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-29/ Vendor Advisory
https://access.redhat.com/errata/RHSA-2026:11805
https://access.redhat.com/errata/RHSA-2026:11813
https://access.redhat.com/errata/RHSA-2026:12264
https://access.redhat.com/errata/RHSA-2026:13342
https://access.redhat.com/errata/RHSA-2026:13412
https://access.redhat.com/errata/RHSA-2026:13533
https://access.redhat.com/errata/RHSA-2026:13582
https://access.redhat.com/errata/RHSA-2026:13583
https://access.redhat.com/errata/RHSA-2026:13596
https://access.redhat.com/errata/RHSA-2026:13600
https://access.redhat.com/errata/RHSA-2026:13665
https://access.redhat.com/errata/RHSA-2026:13682
https://access.redhat.com/errata/RHSA-2026:13683
https://access.redhat.com/errata/RHSA-2026:13922
https://access.redhat.com/errata/RHSA-2026:13977
https://access.redhat.com/errata/RHSA-2026:14223
https://access.redhat.com/errata/RHSA-2026:14303
https://access.redhat.com/errata/RHSA-2026:15889
https://access.redhat.com/errata/RHSA-2026:7671
https://access.redhat.com/errata/RHSA-2026:7672
https://access.redhat.com/errata/RHSA-2026:8052
https://access.redhat.com/errata/RHSA-2026:8459
https://access.redhat.com/errata/RHSA-2026:9345
https://access.redhat.com/errata/RHSA-2026:9638
https://access.redhat.com/security/cve/CVE-2026-5731
https://bugzilla.redhat.com/show_bug.cgi?id=2455901
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-5731.json
Configurations

Configuration 1 (hide)

OR 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:*:*:*:-:*:*:*

History

30 Jun 2026, 03:21

Type Values Removed Values Added
CWE CWE-787
References
  • () https://access.redhat.com/errata/RHSA-2026:11805 -
  • () https://access.redhat.com/errata/RHSA-2026:11813 -
  • () https://access.redhat.com/errata/RHSA-2026:12264 -
  • () https://access.redhat.com/errata/RHSA-2026:13342 -
  • () https://access.redhat.com/errata/RHSA-2026:13412 -
  • () https://access.redhat.com/errata/RHSA-2026:13533 -
  • () https://access.redhat.com/errata/RHSA-2026:13582 -
  • () https://access.redhat.com/errata/RHSA-2026:13583 -
  • () https://access.redhat.com/errata/RHSA-2026:13596 -
  • () https://access.redhat.com/errata/RHSA-2026:13600 -
  • () https://access.redhat.com/errata/RHSA-2026:13665 -
  • () https://access.redhat.com/errata/RHSA-2026:13682 -
  • () https://access.redhat.com/errata/RHSA-2026:13683 -
  • () https://access.redhat.com/errata/RHSA-2026:13922 -
  • () https://access.redhat.com/errata/RHSA-2026:13977 -
  • () https://access.redhat.com/errata/RHSA-2026:14223 -
  • () https://access.redhat.com/errata/RHSA-2026:14303 -
  • () https://access.redhat.com/errata/RHSA-2026:15889 -
  • () https://access.redhat.com/errata/RHSA-2026:7671 -
  • () https://access.redhat.com/errata/RHSA-2026:7672 -
  • () https://access.redhat.com/errata/RHSA-2026:8052 -
  • () https://access.redhat.com/errata/RHSA-2026:8459 -
  • () https://access.redhat.com/errata/RHSA-2026:9345 -
  • () https://access.redhat.com/errata/RHSA-2026:9638 -
  • () https://access.redhat.com/security/cve/CVE-2026-5731 -
  • () https://bugzilla.redhat.com/show_bug.cgi?id=2455901 -
  • () https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-5731.json -

16 Apr 2026, 18:59

Type Values Removed Values Added
CPE cpe:2.3:a:mozilla:thunderbird:149.0.1:*:*:*:-:*:*:*
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:thunderbird:140.9.0:*:*:*:esr:*:*:*
cpe:2.3:a:mozilla:firefox:149.0.1:*:*:*:-:*:*:*
References () 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 - () 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 - Broken Link
References () https://www.mozilla.org/security/advisories/mfsa2026-25/ - () https://www.mozilla.org/security/advisories/mfsa2026-25/ - Vendor Advisory
References () https://www.mozilla.org/security/advisories/mfsa2026-26/ - () https://www.mozilla.org/security/advisories/mfsa2026-26/ - Vendor Advisory
References () https://www.mozilla.org/security/advisories/mfsa2026-27/ - () https://www.mozilla.org/security/advisories/mfsa2026-27/ - Vendor Advisory
References () https://www.mozilla.org/security/advisories/mfsa2026-28/ - () https://www.mozilla.org/security/advisories/mfsa2026-28/ - Vendor Advisory
References () https://www.mozilla.org/security/advisories/mfsa2026-29/ - () https://www.mozilla.org/security/advisories/mfsa2026-29/ - Vendor Advisory
First Time Mozilla
Mozilla firefox
Mozilla thunderbird

13 Apr 2026, 15:17

Type Values Removed Values Added
Summary (en) 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. (en) 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.

07 Apr 2026, 19:16

Type Values Removed Values Added
References
  • () https://www.mozilla.org/security/advisories/mfsa2026-28/ -
  • () https://www.mozilla.org/security/advisories/mfsa2026-29/ -
Summary (en) 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. (en) 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.

07 Apr 2026, 15:17

Type Values Removed Values Added
CVSS v2 : unknown
v3 : unknown
v2 : unknown
v3 : 9.8
CWE CWE-119

07 Apr 2026, 13:16

Type Values Removed Values Added
New CVE

Information

Published : 2026-04-07 13:16

Updated : 2026-07-15 01:16


NVD link : CVE-2026-5731

Mitre link : CVE-2026-5731

CVE.ORG link : CVE-2026-5731


JSON object : View

Products Affected

mozilla

  • firefox
  • thunderbird
CWE
CWE-119

Improper Restriction of Operations within the Bounds of a Memory Buffer

CWE-787

Out-of-bounds Write