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CVE-2026-5731

CRITICAL

9.8

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.

CVE Details

CVSS v3.1 Score9.8

SeverityCRITICAL

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

Attack VectorNETWORK

ComplexityLOW

Privileges RequiredNONE

User InteractionNONE

Published4/7/2026

Last Modified4/7/2026

Sourcenvd

Honeypot Sightings0

Weaknesses (CWE)

CWE-119

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(security@mozilla.org)

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

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

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

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

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

IOC Correlations

No correlations recorded

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