CVE-2026-44064

Executive Summary

CVE-2026-44064 is an out-of-bounds read vulnerability in the ASP (AppleTalk Session Protocol) session ID handling component of Netatalk, an open-source implementation of the Apple Filing Protocol (AFP) and AppleTalk networking stack. The flaw affects versions 1.3 through 4.4.2 and allows an adjacent network attacker to trigger a controlled read beyond allocated memory boundaries by sending a crafted ASP request. This can lead to limited information disclosure (e.g., memory contents) or a denial of service (DoS) condition via application crash. The vulnerability has a CVSS score of 7.1 (High), with an EPSS score of 0.0% indicating low exploitation likelihood at this time. No public exploit code or patch is currently available.

Supply Chain & Package Security

Netatalk is a widely deployed open-source package in Linux distributions, NAS devices, and embedded systems that require AFP support. The vulnerability affects the core ASP library, which is a critical component for session management. Since no patch is available, downstream distributors and system integrators must monitor for updates and consider temporary mitigations. The lack of a GitHub advisory or OSV patch data increases supply chain risk, as users may be unaware of the flaw until an official fix is released.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H
• Base Score: 7.1 (High)
• Attack Vector (AV): Adjacent Network – The attacker must be on the same broadcast domain or link-local network as the target.
• Attack Complexity (AC): Low – No special conditions required.
• Privileges Required (PR): None – No authentication needed.
• User Interaction (UI): None – No user action required.
• Scope (S): Unchanged – The vulnerability does not cross trust boundaries.
• Confidentiality (C): Low – Limited memory disclosure possible.
• Integrity (I): None – No data modification.
• Availability (A): High – Denial of service via crash is likely.

Threat Level: High. While the attack vector is limited to adjacent networks, the low complexity and high availability impact make this a significant risk for internal networks where AFP is used.

Deep Dive & Mechanics

The vulnerability resides in the ASP session ID handling code within Netatalk. ASP is a session-layer protocol used in AppleTalk networks to manage connections between AFP clients and servers. When a client initiates an ASP session, the server allocates a session ID and processes subsequent requests.

The out-of-bounds read occurs when parsing a crafted ASP request that contains a malformed or oversized session ID field. The code fails to validate the length of the session ID against the allocated buffer before reading it. This allows an attacker to read memory beyond the intended buffer, potentially leaking sensitive data or causing a segmentation fault.

Root Cause: Insufficient bounds checking in the ASP session ID parsing routine. The vulnerable code likely uses a fixed-size buffer but does not verify that the incoming session ID length is within that buffer’s bounds.

Attack Flow:

1. Attacker sends a crafted ASP request with an oversized session ID field.
2. The server reads the session ID into a fixed buffer without length validation.
3. The read operation accesses memory beyond the buffer, causing an out-of-bounds read.
4. If the read hits unmapped memory, the server crashes (DoS). If it reads valid memory, the attacker may observe leaked data.

Vulnerable vs. Patched Code

Since no patch is available, the following is a hypothetical comparison based on the vulnerability description.

Vulnerable Code (C pseudocode):

void handle_asp_session_id(uint8_t *packet, size_t packet_len) {
    uint8_t session_id[16]; // Fixed buffer
    // No length check before memcpy
    memcpy(session_id, packet + offset, packet_len - offset);
    // Process session_id...
}

Patched Code (Hypothetical):

void handle_asp_session_id(uint8_t *packet, size_t packet_len) {
    uint8_t session_id[16]; // Fixed buffer
    size_t id_len = packet_len - offset;
    if (id_len > sizeof(session_id)) {
        // Reject oversized session ID
        return;
    }
    memcpy(session_id, packet + offset, id_len);
    // Process session_id...
}

The patch adds a bounds check to ensure the session ID length does not exceed the buffer size before copying.

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• Adjacent network access to a Netatalk server (e.g., same Ethernet segment or Wi-Fi).
• Knowledge of the target’s AFP/ASP port (default 548).
• No authentication required.

Exploitation Steps:

1. Reconnaissance: Scan for AFP servers using Shodan or local network scanning (e.g., nmap -p 548 --open <subnet>).
2. Craft Malicious ASP Request: Use a tool like Scapy or a custom Python script to send a crafted ASP packet with an oversized session ID field.
3. Trigger Vulnerability: Send the crafted packet to the target server.
4. Observe Outcome: Monitor for server crash (DoS) or capture leaked memory data via network analysis.

Example Python Script (Conceptual):

import socket

target_ip = "192.168.1.100"
port = 548

# Craft a malformed ASP request with oversized session ID
# This is a simplified example; actual ASP packet structure is more complex
packet = b"\x00\x01\x00\x00"  # ASP header
packet += b"\xff" * 256       # Oversized session ID

sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.connect((target_ip, port))
sock.send(packet)
response = sock.recv(1024)
print(response)
sock.close()

Note: No public exploit code is available. The above is for educational purposes only.

Blue Team (Defense)

Detection & Prevention:

• Network Segmentation: Restrict AFP access to trusted subnets only.
• Firewall Rules: Block port 548 from untrusted adjacent networks.
• Intrusion Detection: Monitor for malformed ASP packets (see Detection Engineering).
• Memory Protection: Enable ASLR and stack canaries to mitigate exploitation.
• Patch Management: Monitor Netatalk releases for a patch and apply immediately.

Honeypot Deployment: Set up a Netatalk honeypot to capture exploitation attempts and analyze attacker behavior.

Indicators of Compromise (IOCs)

• Network IOCs:
  • ASP packets with session ID fields exceeding 16 bytes.
  • Repeated connection attempts to port 548 from adjacent hosts.
  • Server crashes or restarts on AFP servers.
• Host IOCs:
  • Core dumps from the Netatalk process (e.g., afpd).
  • Log entries indicating segmentation faults or memory access violations.
  • Unusual memory usage patterns in the Netatalk process.

Detection Engineering

YARA Rule

rule CVE_2026_44064_ASP_OOB_Read {
    meta:
        description = "Detects malformed ASP packets with oversized session IDs"
        author = "Valters IT"
        date = "2025-04-10"
        cve = "CVE-2026-44064"
    strings:
        $asp_header = { 00 01 00 00 }  // ASP header magic bytes
        $long_session = { ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff }  // Session ID > 16 bytes
    condition:
        $asp_header at 0 and #long_session > 0
}

Sigma Rule

title: CVE-2026-44064 - ASP Out-of-Bounds Read Attempt
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects network traffic indicative of exploitation attempts against CVE-2026-44064
author: Valters IT
date: 2025-04-10
logsource:
    category: network_connection
    product: suricata
detection:
    selection:
        dest_port: 548
        payload|contains: "ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff"
    condition: selection
falsepositives:
    - Legitimate large session IDs (unlikely)
level: high

Suricata Rule

alert tcp any any -> any 548 (msg:"CVE-2026-44064 ASP Out-of-Bounds Read Attempt"; flow:to_server; content:"|00 01 00 00|"; depth:4; content:"|ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff|"; distance:0; within:256; classtype:attempted-dos; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable AFP/ASP if not required: Stop the afpd service and remove Netatalk from startup.
2. Network Segmentation: Isolate AFP servers on a separate VLAN with strict access controls.
3. Firewall Rules: Block port 548 from all untrusted adjacent networks.
4. Monitor for Updates: Subscribe to Netatalk security advisories and apply patches as soon as released.

Long-Term Fix:

• Apply the official patch from Netatalk when available.
• Consider migrating to SMB/CIFS for file sharing, which is more widely supported and actively maintained.

Workaround:

• Use a reverse proxy or VPN to restrict AFP access to authenticated users only.

Valters IT