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[USN-9013-1] Fetchmail vulnerabilities

Posted on 09 November 2026
Ubuntu Security

==========================================================================Ubuntu Security Notice USN-9013-1
November 09, 2026

fetchmail vulnerabilities
==========================================================================
A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 26.10
- Ubuntu 26.04 LTS
- Ubuntu 24.04 LTS
- Ubuntu 22.04 LTS
- Ubuntu 20.04 LTS
- Ubuntu 18.04 LTS
- Ubuntu 16.04 LTS

Summary:

Several security issues were fixed in Fetchmail.

Software Description:
- fetchmail: SSL enabled POP3, APOP, IMAP mail gatherer/forwarder

Details:

Christian Herdtweck discovered that Fetchmail incorrectly handled certain
long log messages. A remote attacker could possibly use this issue to cause
Fetchmail to crash, resulting in a denial of service. This issue only
affected Ubuntu 16.04 LTS, Ubuntu 18.04 LTS, and Ubuntu 20.04 LTS.
(CVE-2021-36386)

It was discovered that the Fetchmail SMTP client incorrectly handled
certain status code messages. An attacker controlling a malicious server
could possibly use this issue to cause Fetchmail to crash, resulting in a
denial of service. This issue only affected Ubuntu 16.04 LTS, Ubuntu 18.04
LTS, and Ubuntu 20.04 LTS. (CVE-2025-61962)

Tristan Madani discovered that Fetchmail incorrectly handled certain NTLM
authentication challenges. A remote attacker could possibly use this issue
to cause Fetchmail to crash, resulting in a denial of service, or possibly
execute arbitrary code. The default compiler options for affected releases
should reduce the vulnerability to a denial of service. (CVE-2026-94184)

Update instructions:

The problem can be corrected by updating your system to the following
package versions:

Ubuntu 26.10
fetchmail 6.6.6-1ubuntu0.1

Ubuntu 26.04 LTS
fetchmail 6.6.2-2ubuntu0.1

Ubuntu 24.04 LTS
fetchmail 6.4.38-1ubuntu4.2

Ubuntu 22.04 LTS
fetchmail 6.4.27-1ubuntu0.2

Ubuntu 20.04 LTS
fetchmail 6.4.2-2ubuntu0.1~esm1
Available with Ubuntu Pro

Ubuntu 18.04 LTS
fetchmail 6.3.26-3ubuntu0.1~18.04.1+esm1
Available with Ubuntu Pro

Ubuntu 16.04 LTS
fetchmail 6.3.26-2ubuntu0.1~esm1
Available with Ubuntu Pro

In general, a standard system update will make all the necessary changes.

References:
https://ubuntu.com/security/notices/USN-9013-1
CVE-2021-36386, CVE-2025-61962, CVE-2026-94184

Package Information:
https://launchpad.net/ubuntu/+source/fetchmail/6.6.6-1ubuntu0.1
https://launchpad.net/ubuntu/+source/fetchmail/6.6.2-2ubuntu0.1
https://launchpad.net/ubuntu/+source/fetchmail/6.4.38-1ubuntu4.2
https://launchpad.net/ubuntu/+source/fetchmail/6.4.27-1ubuntu0.2

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