What’s Vulnerable › Vulnerabilities

CVE-2021-38496

• Severity: high (CVSS 8.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.7% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-11-03 · updated 2026-06-17
• Weakness: CWE-416

Description

During operations on MessageTasks, a task may have been removed while it was still scheduled, resulting in memory corruption and a potentially exploitable crash. This vulnerability affects Thunderbird < 78.15, Thunderbird < 91.2, Firefox ESR < 91.2, Firefox ESR < 78.15, and Firefox < 93.

Affected products

• Debian Linux: 9.0, 10.0, 11.0
• Mozilla Firefox: before 93.0; from 91.0 before 91.2 — fixed in 91.2, 93.0
• Mozilla Firefox ESR: before 78.15 — fixed in 78.15
• Mozilla Thunderbird: before 78.15; from 91.0 before 91.2 — fixed in 78.15, 91.2

How to fix

Upgrade to a fixed version: Mozilla Firefox 91.2, 93.0; Mozilla Firefox ESR 78.15; Mozilla Thunderbird 78.15, 91.2. Check the vendor advisory for mitigations.

References

• https://bugzilla.mozilla.org/show_bug.cgi?id=1725335
• https://lists.debian.org/debian-lts-announce/2022/01/msg00001.html
• https://www.debian.org/security/2022/dsa-5034
• https://www.mozilla.org/security/advisories/mfsa2021-43/
• https://www.mozilla.org/security/advisories/mfsa2021-44/
• https://www.mozilla.org/security/advisories/mfsa2021-45/
• https://www.mozilla.org/security/advisories/mfsa2021-46/
• https://www.mozilla.org/security/advisories/mfsa2021-47/
• https://bugzilla.mozilla.org/show_bug.cgi?id=1725335
• https://lists.debian.org/debian-lts-announce/2022/01/msg00001.html
• https://www.debian.org/security/2022/dsa-5034
• https://www.mozilla.org/security/advisories/mfsa2021-43/

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