CVE-2026-34578: OPNsense has an LDAP Injection via Unsanitized Username in Authentication

Severity: high (CVSS 8.2 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2026-04-09 · updated 2026-10-26
Weakness: CWE-90

Description

OPNsense is a FreeBSD based firewall and routing platform. Prior to 26.1.6, OPNsense's LDAP authentication connector passes the login username directly into an LDAP search filter without calling ldap_escape(). An unauthenticated attacker can inject LDAP filter metacharacters into the username field of the WebGUI login page to enumerate valid LDAP usernames in the configured directory. When the LDAP server configuration includes an Extended Query to restrict login to members of a specific group, the same injection can be used to bypass that group membership restriction and authenticate as any LDAP user whose password is known, regardless of group membership. This vulnerability is fixed in 26.1.6.

Affected products

OPNsense: before 26.1.6 — fixed in 26.1.6

How to fix

Upgrade to a fixed version: OPNsense 26.1.6. Check the vendor advisory for mitigations.

References

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