LDAP injection in Dovecot and OX Dovecot Pro - CVE-2026-27860
Published: April 1, 2026
Vulnerability identifier: #VU124725
CSH Severity: Medium
CVSS v4: 6.3 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-27860
CWE-ID: CWE-90
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to bypass authentication.
The vulnerability exists due to improper neutralization of special elements in an LDAP query within the auth-ldap module when processing usernames. A remote attacker can send a specially crafted request with malicious username when auth_username_chars is empty to probe LDAP structure and potentially bypass authentication.
The server must have auth_username_chars configuration option cleared.
Affected software
Dovecot
OX Dovecot Pro
Ubuntu
dovecot (Ubuntu package)
OX Dovecot Pro
Ubuntu
dovecot (Ubuntu package)
How to mitigate CVE-2026-27860
Install security update from vendor's website.
Dovecot - update to 2.4.3
OX Dovecot Pro - update to 3.1.4
dovecot (Ubuntu package) - addressed in versions 1:2.3.16+dfsg1-3ubuntu2.7, 1:2.3.16+dfsg1-3ubuntu2.8, 1:2.3.21+dfsg1-2ubuntu6.3, 1:2.3.21+dfsg1-2ubuntu6.4, 1:2.4.1+dfsg1-5ubuntu4.1
OX Dovecot Pro - update to 3.1.4
dovecot (Ubuntu package) - addressed in versions 1:2.3.16+dfsg1-3ubuntu2.7, 1:2.3.16+dfsg1-3ubuntu2.8, 1:2.3.21+dfsg1-2ubuntu6.3, 1:2.3.21+dfsg1-2ubuntu6.4, 1:2.4.1+dfsg1-5ubuntu4.1