CVE-2026-44074: Netatalk DOS Vulnerability

CVE-2026-44074 Overview

CVE-2026-44074 affects Netatalk versions 2.1.0 through 4.4.2. The flaw resides in error-handling logic that combines multiple errno values using a bitwise OR operation. When several error conditions occur simultaneously, the resulting value does not map to a valid errno, causing the daemon to follow incorrect error-handling paths. A remote attacker who can reach the service may trigger conditions that produce minor service disruption. The issue is categorized under [CWE-682] Incorrect Calculation. No public exploit is available, and the vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog.

Critical Impact

Remote attackers can trigger incorrect error-handling paths in Netatalk, resulting in limited availability impact on the affected service.

Affected Products

• Netatalk 2.1.0 through 4.4.2
• AFP (Apple Filing Protocol) services running on affected Netatalk builds
• Network-attached storage and Linux/BSD systems deploying Netatalk for macOS file sharing

Discovery Timeline

• 2026-05-21 - CVE-2026-44074 published to NVD
• 2026-05-21 - Last updated in NVD database

Technical Details for CVE-2026-44074

Vulnerability Analysis

Netatalk implements the Apple Filing Protocol (AFP) for file sharing between Unix-like systems and macOS clients. The vulnerability arises in code paths where multiple error conditions can occur concurrently during request processing. The implementation merges several errno values using a bitwise OR (|) operator rather than selecting a single canonical error code. The resulting integer often does not correspond to any defined POSIX error constant.

Downstream handlers interpret this composite value as a valid errno. They then dispatch the wrong error-handling routine. The outcome is inconsistent service behavior and possible minor disruption of the AFP service. Confidentiality and integrity are not affected. The attack does not require authentication, but exploitation requires specific timing to trigger multiple concurrent error conditions, which limits practical impact.

Root Cause

The root cause is an incorrect calculation [CWE-682] in error aggregation. errno values are discrete integers, not bit flags. Combining them with bitwise OR produces meaningless values. Correct logic must select a single representative error code or map composite states explicitly.

Attack Vector

The attack vector is network-based. A remote, unauthenticated attacker sends crafted AFP traffic designed to provoke multiple simultaneous error conditions in a single request. The attack complexity is high because the attacker must reliably trigger concurrent errors. Successful exploitation degrades availability of the AFP service without compromising data.

No verified exploit code is publicly available. Refer to the Netatalk Security Advisory for protocol-level details.

Detection Methods for CVE-2026-44074

Indicators of Compromise

• Unexpected termination or restart events for the afpd or netatalk service processes
• AFP client sessions disconnecting with anomalous or undefined error codes
• Log entries containing errno values that do not match standard POSIX constants
• Spikes in malformed or rapidly repeated AFP requests from a single source

Detection Strategies

• Monitor Netatalk service logs for abnormal error reporting patterns and frequent session failures
• Inspect network traffic to TCP port 548 for atypical request bursts that could induce concurrent error conditions
• Correlate AFP service crashes with preceding network activity from the same client IP

Monitoring Recommendations

• Enable verbose Netatalk logging and forward afpd logs to a centralized log management platform
• Alert on repeated service restarts of netatalk or afpd within short time windows
• Track baseline AFP error rates and trigger alerts on statistically significant deviations

How to Mitigate CVE-2026-44074

Immediate Actions Required

• Identify all hosts running Netatalk versions 2.1.0 through 4.4.2 across the environment
• Restrict access to TCP port 548 using firewall rules so only trusted clients can reach the AFP service
• Upgrade Netatalk to a fixed release as published in the vendor advisory
• Review service logs for prior occurrences of anomalous errno values or unexplained restarts

Patch Information

Consult the Netatalk Security Advisory for the official fixed versions and patch commits. Apply vendor-supplied updates through the operating system package manager or by rebuilding from source once a fixed release is available.

Workarounds

• Limit AFP service exposure to trusted network segments using host-based and perimeter firewalls
• Disable Netatalk on systems that do not require AFP file sharing
• Where feasible, migrate macOS clients to SMB-based file sharing as an interim measure

# Configuration example: restrict AFP (port 548) to a trusted subnet
iptables -A INPUT -p tcp --dport 548 -s 10.0.0.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 548 -j DROP