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

What is CVE-2026-57962?

CVE-2026-57962 is a medium-severity denial of service vulnerability in Mozilla Thunderbird, published on 1 Jul 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

Official 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.

Weakness: CWE-400

Which versions are affected by CVE-2026-57962?

It affects 1 product.

Products include Mozilla Thunderbird.

How do I fix CVE-2026-57962?

Upgrade to a fixed version.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2026-57962 being exploited?

There is no known exploitation of CVE-2026-57962 in the wild and no public exploit code.

Other vulnerabilities in Mozilla Thunderbird

• CVE-2026-92238 Ambiguous parsing of mail headers Critical 9.8
• CVE-2026-84637 Calendar invitation attachments could launch local executables Critical 9.8
• CVE-2021-43529 Memory corruption in Thunderbird Critical 9.8
• CVE-2019-11703 Memory corruption in Thunderbird Critical 9.8
• CVE-2019-11704 Memory corruption in Thunderbird Critical 9.8

All Mozilla Thunderbird vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as DEBIAN-CVE-2026-57962, GHSA-qg45-rc8c-9676, UBUNTU-CVE-2026-57962.