CVE-2015-3223

What it actually does

The vulnerability causes an infinite loop in the ldb_wildcard_compare function within ldb_match.c when processing certain zero values in LDAP wildcard comparisons, allowing remote attackers to trigger a denial of service via crafted network packets against the Active Directory LDAP server.

Why it matters to the business

Successful exploitation can render directory services unavailable, disrupting authentication, authorization, and resource access for any systems or users relying on the Samba-based Active Directory environment, leading to operational downtime.

How an attack unfolds

An attacker crafts malicious LDAP packets targeting the Samba Active Directory server and sends them over the network; the ldb library mishandles zero values during wildcard matching, entering an infinite loop that consumes resources and denies service to legitimate users.

How to fix it

Upgrade Samba to version 4.1.22 or later for the 4.1.x branch, 4.2.7 or later for the 4.2.x branch, or 4.3.3 or later for the 4.3.x branch; apply vendor patches addressing ldb before 1.1.24.

How to confirm the fix worked

Confirm Samba and ldb versions meet or exceed the fixed releases, then test LDAP operations with edge-case wildcard queries containing zero values to ensure no infinite loop occurs.

Typical attack path

1. Identify exposed Samba AD LDAP service
2. Craft packets containing specific zero values for wildcard comparisons
3. Transmit packets to trigger infinite loop in ldb_match.c
4. Observe service degradation or crash

How to detect it

Review Samba and LDAP server logs for repeated malformed query patterns, monitor for sustained high CPU utilization on the directory service process without corresponding legitimate traffic volume.

What your security team should do

• Prioritize upgrade of all Samba instances to the fixed versions listed
• Restrict network access to LDAP ports to trusted sources until patched
• Monitor CPU and resource usage on AD servers for anomalous spikes