CVE-2026-27860
Received Received - Intake
LDAP Injection in Dovecot Authentication Allows Access Bypass

Publication date: 2026-03-27

Last updated on: 2026-04-29

Assigner: Open-Xchange

Description
If auth_username_chars is empty, it is possible to inject arbitrary LDAP filter to Dovecot's LDAP authentication. This leads to potentially bypassing restrictions and allows probing of LDAP structure. Do not clear out auth_username_chars, or install fixed version. No publicly available exploits are known.
CVSS Scores
EPSS Scores
Probability:
Percentile:
Meta Information
Published
2026-03-27
Last Modified
2026-04-29
Generated
2026-06-16
AI Q&A
2026-03-27
EPSS Evaluated
2026-06-15
NVD
CVE-2026-27860
EUVD
EUVD-2026-16573
Affected Vendors & Products
Showing 2 associated CPEs
Vendor Product Version / Range
dovecot dovecot to 2.4.3 (exc)
open-xchange dovecot to 3.1.4 (exc)
Helpful Resources
Exploitability
CWE
CWE Icon
KEV
KEV Icon
CWE ID Description
CWE-90 The product constructs all or part of an LDAP query using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended LDAP query when it is sent to a downstream component.
Attack-Flow Graph
AI Quick Actions
Instant insights powered by AI
Executive Summary

This vulnerability occurs when the configuration parameter auth_username_chars is empty in Dovecot's LDAP authentication. In this case, it becomes possible to inject arbitrary LDAP filters, which can bypass certain restrictions and allow an attacker to probe the LDAP directory structure.

Impact Analysis

The vulnerability can potentially allow an attacker to bypass authentication restrictions and gain unauthorized insight into the LDAP directory structure. However, no publicly available exploits are known, and the impact is limited to information disclosure with a low severity score.

Mitigation Strategies

To mitigate this vulnerability, do not clear out the auth_username_chars setting in Dovecot's LDAP authentication configuration.

Alternatively, install a fixed version of Dovecot that addresses this issue.

Chat Assistant
Ask questions about this CVE
Hi! I’m here to help you understand CVE-2026-27860. Ask me anything about the vulnerability, its impact, or mitigation strategies.
0/70
EPSS Chart