CVE-2026-44056: Netatalk Buffer Overflow Vulnerability

CVE-2026-44056 Overview

CVE-2026-44056 is a stack-based buffer overflow [CWE-121] in desktop.c within Netatalk, an open source implementation of the Apple Filing Protocol (AFP). The flaw affects Netatalk versions 1.3 through 4.2.2. A remote authenticated attacker can trigger the overflow to cause a denial of service, obtain limited information from process memory, or modify limited data on the host. Exploitation requires valid credentials on the AFP service and involves high attack complexity, which constrains broad opportunistic abuse. Netatalk is widely deployed on Linux and BSD file servers that provide Mac clients with network file shares, making any authenticated AFP user a potential threat actor.

Critical Impact

Authenticated attackers can corrupt the stack of the Netatalk daemon to crash the service, leak limited memory contents, or tamper with limited data served to AFP clients.

Affected Products

• Netatalk 1.3 through 4.2.2
• desktop.c component of the Netatalk AFP daemon
• Linux and BSD distributions packaging vulnerable Netatalk releases

Discovery Timeline

• 2026-05-21 - CVE-2026-44056 published to NVD
• 2026-05-21 - Last updated in NVD database

Technical Details for CVE-2026-44056

Vulnerability Analysis

The vulnerability resides in desktop.c, a source file that implements desktop database handling for the Netatalk AFP server. A stack-allocated buffer in this code path is written without enforcing a strict upper bound against attacker-influenced input length. When an authenticated AFP client supplies a request that exceeds the expected size, the surplus bytes overwrite adjacent stack memory in the server process.

The consequences listed in the advisory are bounded: denial of service through process crash, limited information disclosure, and limited data modification. The constrained confidentiality and integrity impact suggests the overflow corrupts a narrow region of the stack rather than enabling full control-flow hijacking. Network reachability combined with the requirement for valid credentials means the threat surface includes any user with an AFP account, including low-privilege guest-like accounts on shared systems.

Root Cause

The root cause is missing or insufficient length validation on data copied into a fixed-size stack buffer in desktop.c. This is a classic [CWE-121] stack-based buffer overflow pattern where input boundaries are not enforced before a memory copy operation.

Attack Vector

The attack vector is network-based and requires authentication. An attacker first authenticates to the Netatalk AFP service using valid credentials. The attacker then issues a crafted AFP request targeting the desktop database functionality in desktop.c. The oversized input overwrites stack memory inside the Netatalk worker process, producing one of the documented outcomes. High attack complexity indicates non-trivial conditions, such as specific request sequencing or memory state, must align for reliable exploitation.

No public proof-of-concept exploit code is referenced in the advisory. Readers should consult the Netatalk Security Advisory CVE-2026-44056 for vendor technical details.

Detection Methods for CVE-2026-44056

Indicators of Compromise

• Unexpected crashes or restarts of the afpd or netatalk daemon, especially with stack smashing protector messages in system logs.
• Core dumps generated by Netatalk worker processes after authenticated AFP sessions.
• Authenticated AFP sessions originating from unusual source addresses immediately preceding daemon termination.

Detection Strategies

• Monitor system logs for afpd segmentation faults, __stack_chk_fail messages, or abnormal child process exits tied to AFP connections.
• Correlate AFP authentication events with subsequent service restarts to identify abusive accounts.
• Inspect packet captures on TCP port 548 for malformed or oversized AFP desktop database requests.

Monitoring Recommendations

• Enable verbose Netatalk logging and forward afpd logs to a centralized log platform for retention and alerting.
• Track per-user AFP session counts and failure rates to surface accounts repeatedly causing daemon faults.
• Alert on any Netatalk service restart that occurs within seconds of a successful AFP login event.

How to Mitigate CVE-2026-44056

Immediate Actions Required

• Upgrade Netatalk to a fixed release published after version 4.2.2 as identified in the vendor advisory.
• Restrict AFP service exposure to trusted network segments using firewall rules on TCP port 548.
• Audit AFP accounts and disable unused or shared credentials to reduce the authenticated attack surface.

Patch Information

Refer to the Netatalk Security Advisory CVE-2026-44056 for the authoritative list of patched versions and source commits. Apply distribution-provided updates for Netatalk packages on affected Linux and BSD systems as soon as they are available.

Workarounds

• Disable the Netatalk AFP service on hosts where AFP file sharing is not required.
• Block inbound connections to TCP port 548 at the perimeter and host firewalls except from explicitly authorized clients.
• Enforce strong, unique passwords for all AFP accounts and remove guest access if previously enabled.

# Configuration example: restrict AFP access at the host firewall (iptables)
iptables -A INPUT -p tcp --dport 548 -s 10.0.0.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 548 -j DROP

# Disable the Netatalk service if AFP is not needed
systemctl stop netatalk
systemctl disable netatalk