CVE-2026-44054: Netatalk AFP Session DoS Vulnerability

CVE-2026-44054 Overview

CVE-2026-44054 affects Netatalk versions 2.0.0 through 4.4.2. Netatalk is an open-source implementation of the Apple Filing Protocol (AFP) used to share files between Unix-like systems and macOS clients. The flaw stems from AFP session tokens derived from predictable process identifiers (PIDs). A remote authenticated attacker can abuse the reconnect mechanism to trigger a denial of service against the AFP daemon. The weakness is tracked under CWE-330: Use of Insufficiently Random Values.

Critical Impact
An authenticated remote attacker can disrupt AFP file sharing services by hijacking or invalidating reconnect tokens generated from guessable process IDs.

Affected Products

Netatalk 2.0.0 through 2.x
Netatalk 3.x releases
Netatalk 4.0.0 through 4.4.2

Discovery Timeline

2026-05-21 - CVE-2026-44054 published to NVD
2026-05-21 - Last updated in NVD database

Technical Details for CVE-2026-44054

Vulnerability Analysis

Netatalk implements an AFP reconnect feature that allows clients to resume a session after a network interruption. The daemon issues a session token that the client presents to reattach to its prior session state. In affected versions, this token is derived from the process ID of the session handler. PIDs are sequential, small integers, and observable on most systems, making them poor sources of entropy. An authenticated attacker who can predict or enumerate token values can submit reconnect requests targeting sessions that belong to other users. The reconnect handler tears down or replaces the legitimate session, removing service availability for the affected user. Because the attack only requires valid AFP credentials and standard network reachability, the operational barrier is low for any environment with multiple authenticated users.

Root Cause

The root cause is the use of an insufficiently random value (CWE-330) for security-relevant identifiers. The AFP server constructs reconnect tokens from process IDs rather than from a cryptographically secure random number generator. Sequential PIDs provide a limited and predictable keyspace, so a token guessing strategy is feasible without brute-forcing the full token field.

Attack Vector

The attack requires network access to the AFP service and valid low-privilege credentials. The attacker enumerates plausible PID values, crafts reconnect requests carrying forged tokens, and submits them to the server. When a guessed token matches an active session, the daemon processes the reconnect and disrupts the legitimate client. Repeated attempts produce a sustained denial of service against arbitrary users. No user interaction is required on the victim side. Confidentiality and integrity are not directly impacted because the token does not unlock authenticated data access on its own. Availability is the primary loss, consistent with the CVSS impact metrics.

The vulnerability mechanism is described in prose because no verified proof-of-concept code has been published. Refer to the Netatalk Security Advisory for vendor technical detail.

Detection Methods for CVE-2026-44054

Indicators of Compromise

Unexpected AFP session terminations correlated with reconnect requests from unfamiliar source addresses.
Repeated reconnect attempts from a single authenticated principal targeting tokens that do not belong to that principal.
Abnormal volume of afpd child process restarts in system logs.

Detection Strategies

Inspect afpd and syslog entries for repeated reconnect failures and session resets clustered in short time windows.
Correlate AFP authentication events with subsequent reconnect events to identify users who repeatedly invoke reconnects without prior disconnect activity.
Baseline normal reconnect frequency per user and alert on deviations.

Monitoring Recommendations

Forward Netatalk logs to a centralized logging or SIEM platform for cross-host correlation.
Monitor network flow telemetry on TCP port 548 for bursts of short-lived connections from a single source.
Alert on AFP daemon crashes, restarts, or sustained high process churn on file servers.

How to Mitigate CVE-2026-44054

Immediate Actions Required

Inventory all hosts running Netatalk and identify versions in the 2.0.0 through 4.4.2 range.
Restrict AFP service exposure to trusted network segments and authenticated users only.
Review AFP user accounts and disable any that are not actively required.

Patch Information

Apply the fixed release published by the Netatalk project. Refer to the Netatalk Security Advisory for CVE-2026-44054 for the patched version numbers and upgrade instructions. Upgrade all instances above the 4.4.2 boundary once a corrected build is available from your distribution or the upstream project.

Workarounds

Disable the AFP reconnect feature in afp.conf if your client population does not depend on session resumption.
Block external access to TCP port 548 at the perimeter and limit AFP to internal management networks.
Migrate file shares to SMB where feasible and decommission AFP on hosts that do not require Apple Filing Protocol support.

bash

# Example: restrict AFP reconnect behavior in afp.conf
[Global]
    sleep time = 0
    disconnect time = 0
    # Limit AFP to a trusted interface
    afp listen = 10.0.0.5