How severe is CVE-2026-34578?

CVE-2026-34578 has a CVSS 3.x base score of 8.2, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity low, and availability none.

Is CVE-2026-34578 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (33rd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-34578?

CVE-2026-34578 affects Opnsense. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-34578?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

Does CVE-2026-34578 have an EU (EUVD) identifier?

Yes. CVE-2026-34578 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-20896.

When was CVE-2026-34578 published?

CVE-2026-34578 was published on 2026-04-09 and last updated on 2026-06-17.

CVE-2026-34578

CVE-2026-34578 is a high-severity vulnerability in Opnsense with a CVSS 3.x base score of 8.2. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-90.

Key facts

Severity: High (CVSS 3.x base score 8.2)
EPSS exploit prediction: 0% (33rd percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-20896
Weakness: CWE-90
Affected product: Opnsense
Published: 2026-04-09
Last modified: 2026-06-17

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.

Frequently asked questions

What is CVE-2026-34578?: 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.
How severe is CVE-2026-34578?: CVE-2026-34578 has a CVSS 3.x base score of 8.2, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity low, and availability none.
Is CVE-2026-34578 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (33rd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-34578?: CVE-2026-34578 affects Opnsense. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-34578?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2026-34578 have an EU (EUVD) identifier?: Yes. CVE-2026-34578 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-20896.
When was CVE-2026-34578 published?: CVE-2026-34578 was published on 2026-04-09 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:opnsense:opnsense:*:*:*:*:*:*:*:*

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