CVE-2026-5731

CRITICAL EPSS 25.5%
Published Apr 7, 20262mo ago · Modified Jun 17, 20261w ago
9.8 CVSS 3.1
Critical
Find Similar
Published Apr 7, 2026 2mo ago
Last Modified Jun 17, 2026 1w ago

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.

CVSS Details

Base Score
9.8
Exploitability
3.9
Impact
5.9
Vector string
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Attack Vector Network
Attack Complexity Low
Privileges Required None
User Interaction None
Scope Unchanged
Confidentiality High
Integrity High
Availability High

Threat Intelligence

EPSS Exploit Probability
25.5% percentile
Exploit & Patch Status
No Known Exploit
No Patch Available

Weaknesses 1

CWE-119 Improper Restriction of Operations within the Bounds of a Memory Buffer Memory Safety

Affected Products 5

VendorProductVersionRange
mozillafirefox115.34.0any
mozillafirefox140.9.0any
mozillafirefox149.0.1any
mozillathunderbird140.9.0any
mozillathunderbird149.0.1any

References 6

  • bugzilla.mozilla.org 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
  • mozilla.org https://www.mozilla.org/security/advisories/mfsa2026-25/
    Vendor Advisory
  • mozilla.org https://www.mozilla.org/security/advisories/mfsa2026-26/
    Vendor Advisory
  • mozilla.org https://www.mozilla.org/security/advisories/mfsa2026-27/
    Vendor Advisory
  • mozilla.org https://www.mozilla.org/security/advisories/mfsa2026-28/
    Vendor Advisory
  • mozilla.org https://www.mozilla.org/security/advisories/mfsa2026-29/
    Vendor Advisory

Remediation

No remediation data recorded yet

Check vendor advisories and the NVD entry for patch availability.