LDAP Authentication Bypass Vulnerability in OPNsense Firewall
CVE-2026-34578

8.2HIGH

Key Information:

Vendor

Opnsense

Status
Core
Vendor
CVE Published:
9 April 2026

What is CVE-2026-34578?

The OPNsense Firewall, a FreeBSD-based platform, has a vulnerability in its LDAP authentication connector where it improperly handles user input. Specifically, prior to version 26.1.6, the software incorporates unsanitized usernames into LDAP search filters, allowing unauthenticated attackers to manipulate queries. This vulnerability can lead to the enumeration of valid LDAP usernames from the configured directory. Furthermore, if the LDAP server is set to limit access by group membership, attackers can exploit this flaw to bypass those restrictions and impersonate any LDAP user, provided their password is known. Users are recommended to update to the latest version to mitigate these security risks.

Affected Version(s)

core < 26.1.6

References

https://github.com/opnsense/core/security/advisories/GHSA...
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https://github.com/opnsense/core/commit/016f66cb4620cd481...
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CVSS V3.1

Score:
8.2
Severity:
HIGH
Confidentiality:
High
Integrity:
Low
Availability:
High
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

.