CVE-2026-57962: Denial-of-service via malicious LDAP address-book server

Severity: medium (CVSS 5.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-07-01 · updated 2026-10-25
Weakness: CWE-400

Description

A malicious LDAP server, which a Thunderbird user is configured to query for address-book autocomplete, can stash arbitrarily large amounts of attacker-supplied data into the Thunderbird LDAP client until it crashes due to memory exhaustion. This vulnerability was fixed in Thunderbird 152.0.1 and Thunderbird 140.12.1.

Affected products

Mozilla Thunderbird: before 140.12.1; before 152.0.1 — fixed in 140.12.1, 152.0.1

How to fix

Upgrade to a fixed version: Mozilla Thunderbird 140.12.1, 152.0.1. Check the vendor advisory for mitigations.

References

https://bugzilla.mozilla.org/show_bug.cgi?id=2042872
https://www.mozilla.org/security/advisories/mfsa2026-63/
https://www.mozilla.org/security/advisories/mfsa2026-64/

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