CVE-2026-35563: Apache Directory LDAP API: LDAP client implementation does not verify if the server certificate matches the intended LDAP hostname

[Emmanuel Lécharny <elecharny () apache org>]

Severity: important 

Affected versions:

- Apache Directory LDAP API (org.apache.directory.api:api-ldap-client-api) 2.0.0 through 2.1.7

Description:

It was identified that the LDAP client implementation in version 2.1.7 does not verify if the server certificate 
matches the intended LDAP 
hostname. While the underlying code validates the certificate chain 
against a trusted authority, the absence of endpoint identification 
allows a valid certificate issued for an entirely unrelated host to be 
improperly accepted. This oversight leaves the connection highly 
vulnerable to server impersonation and complete connection compromise.


The
 root cause of this vulnerability lies in the incomplete TLS server 
identity verification within the LDAP client implementation.




The attacker requires MITM capability on the network to exploit this vulnerability. This attacker must be able to 
present a certificate trusted by the client's configured trust store.




The hostname verification has been enforced in the new version of the LDAP API

Credit:

Rafał Łykowski and Łukasz Kollbek of Qualtrics (finder)

References:

https://directory.apache.org/
https://www.cve.org/CVERecord?id=CVE-2026-35563