CVE-2026-5731

Published: Apr 7, 2026Modified: Jul 15, 2026

9.8

Vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Exploitability: 3.9 / Impact: 5.9

Source: 134c704f-9b21-4f2e-91b3-4a467353bcc0 (Secondary)

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 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.

Affected (5)

Products: Mozilla: Firefox, Thunderbird

2 products

Configuration A

5 vulnerable

Vulnerable Software	Affected Versions
Mozilla Firefox	Version 115.34.0
Mozilla Firefox	Version 140.9.0
Mozilla Firefox	Version 149.0.1
Mozilla Thunderbird	Version 140.9.0
Mozilla Thunderbird	Version 149.0.1

Related CWEs

Improper Restriction of Operations within the Bounds of a Memory Buffer

The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.

Out-of-bounds Write

The product writes data past the end, or before the beginning, of the intended buffer.

References (33)

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

Source: security@mozilla.org

Broken Link

https://www.mozilla.org/security/advisories/mfsa2026-25/

Source: security@mozilla.org

Vendor Advisory

https://www.mozilla.org/security/advisories/mfsa2026-26/

Source: security@mozilla.org

Vendor Advisory

https://www.mozilla.org/security/advisories/mfsa2026-27/

Source: security@mozilla.org

Vendor Advisory

https://www.mozilla.org/security/advisories/mfsa2026-28/

Source: security@mozilla.org

Vendor Advisory

https://www.mozilla.org/security/advisories/mfsa2026-29/

Source: security@mozilla.org

Vendor Advisory

https://access.redhat.com/errata/RHSA-2026:11805

Source: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c

https://access.redhat.com/errata/RHSA-2026:11813

Source: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c

https://access.redhat.com/errata/RHSA-2026:12264

Source: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c

https://access.redhat.com/errata/RHSA-2026:13342

Source: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c

https://access.redhat.com/errata/RHSA-2026:13412

Source: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c

https://access.redhat.com/errata/RHSA-2026:13533

Source: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c

https://access.redhat.com/errata/RHSA-2026:13582

Source: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c

https://access.redhat.com/errata/RHSA-2026:13583

Source: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c

https://access.redhat.com/errata/RHSA-2026:13596

Source: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c

https://access.redhat.com/errata/RHSA-2026:13600

Source: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c

https://access.redhat.com/errata/RHSA-2026:13665

Source: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c

https://access.redhat.com/errata/RHSA-2026:13682

Source: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c

https://access.redhat.com/errata/RHSA-2026:13683

Source: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c

https://access.redhat.com/errata/RHSA-2026:13922

Source: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c

https://access.redhat.com/errata/RHSA-2026:13977

Source: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c

https://access.redhat.com/errata/RHSA-2026:14223

Source: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c

https://access.redhat.com/errata/RHSA-2026:14303

Source: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c

https://access.redhat.com/errata/RHSA-2026:15889

Source: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c

https://access.redhat.com/errata/RHSA-2026:7671

Source: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c

https://access.redhat.com/errata/RHSA-2026:7672

Source: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c

https://access.redhat.com/errata/RHSA-2026:8052

Source: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c

https://access.redhat.com/errata/RHSA-2026:8459

Source: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c

https://access.redhat.com/errata/RHSA-2026:9345

Source: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c

https://access.redhat.com/errata/RHSA-2026:9638

Source: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c

https://access.redhat.com/security/cve/CVE-2026-5731

Source: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c

https://bugzilla.redhat.com/show_bug.cgi?id=2455901

Source: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c

https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-5731.json

Source: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c

Timeline

No history available yet.