Debian Dovecot High Severity Service Disruption Info Leak Flaw DLA-4617-1
debian lts
June 5, 2026
Multiple vulnerabilities were discovered in dovecot, a POP3/IMAP server, which could lead to Denial of Service or information leak
Topics Covered
Summary
CVE-2026-33603
An attacker can use a specially crafted base64 exchange between
Dovecot and Client to fake SCRAM TLS channel binding and later
eavesdrop communications between Dovecot and client as MITM proxy.
CVE-2026-40020
An attacker can use the IMAP `SETACL` command to inject the anyone
permission to user's dovecot-acl file even if
`imap_acl_allow_anyone=no`, thereby allowing folders to be spammed
to all users. (The impact was limited to being able to spam folders
to other users. No unexpected access is gained.)
CVE-2026-42006
An attacker can cause uncontrolled memory usage with excessive
bracing over IMAP. This stems from an incomplete fix for
CVE-2026-27857.
For Debian 11 bullseye, these problems have been fixed in version
1:2.3.13+dfsg1-2+deb11u4.
We recommend that you upgrade your dovecot packages.
For the detailed security status of dovecot please refer to
its security tracker page at:
https://security-tracker.debian.org/tracker/dovecot
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Severity
important
Lowest
Low
Medium
High
Critical
Package: dovecot
Version: 1:2.3.13+dfsg1-2+deb11u4
CVE ID: CVE-2026-33603 CVE-2026-40020 CVE-2026-42006
Debian Bug: 1136444
Topics Covered
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