CVE-2026-44057

Executive Summary

CVE-2026-44057 is a low-severity vulnerability in the Netatalk open-source implementation of the Apple Filing Protocol (AFP). The flaw resides in the Spotlight RPC unmarshaller, where a dead bounds check creates an unreachable code path. This means the bounds validation logic is present in the source code but is never executed due to a logical error, leaving the system with no effective bounds protection. A remote authenticated attacker can exploit this by sending crafted Spotlight RPC requests, potentially leading to limited information disclosure. The vulnerability affects Netatalk versions 3.0.0 through 4.4.2. No public exploit code or patch is currently available.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It affects the Netatalk software package, which is commonly distributed via Linux package managers (e.g., apt, yum) and source code repositories.

CVSS Breakdown & Threat Level

• CVSS Score: 3.1 (Low)
• Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
• Attack Vector: Network (AV:N) – The vulnerability can be exploited remotely.
• Attack Complexity: Low (AC:L) – No special conditions are required for exploitation.
• Privileges Required: Low (PR:L) – An attacker must have valid authentication credentials.
• User Interaction: None (UI:N) – No user action is required.
• Scope: Unchanged (S:U) – The vulnerability does not affect other components.
• Confidentiality Impact: Low (C:L) – Limited information disclosure is possible.
• Integrity Impact: None (I:N) – No data modification is possible.
• Availability Impact: None (A:N) – No denial of service is possible.

Threat Level: Low. The requirement for authentication and the limited impact reduce the immediate risk. However, the lack of a patch means that all affected versions remain vulnerable.

Deep Dive & Mechanics

The vulnerability is located in the Spotlight RPC unmarshaller component of Netatalk. Spotlight is a file system indexing and search technology used by macOS. Netatalk implements this protocol to allow macOS clients to search for files on AFP shares.

The issue is a "dead bounds check." In the source code, a bounds check is written to validate the size of incoming data from a Spotlight RPC request. However, due to a logical error (e.g., incorrect comparison operator, wrong variable, or misplaced code), this check is never reached during execution. The code path containing the check is unreachable, meaning the data is processed without any size validation.

This allows an attacker to send a crafted Spotlight RPC request with an oversized or malformed payload. The unmarshaller will process this data without proper bounds checking, potentially reading beyond the allocated buffer. This can lead to the disclosure of adjacent memory contents, which may contain sensitive information such as file metadata, other users' data, or system information.

The vulnerability is classified under CWE-754 (Improper Check for Unusual or Exceptional Conditions), as the software fails to properly handle a condition that should trigger a bounds check.

Vulnerable vs. Patched Code

Since no patch is available, a direct comparison is not possible. However, the vulnerable code pattern can be described:

Vulnerable Code (Conceptual):

// In the Spotlight RPC unmarshaller
void unmarshal_spotlight_request(uint8_t *data, size_t len) {
    // Dead bounds check - never reached
    if (0) { // This condition is always false
        if (len > MAX_SPOTLIGHT_SIZE) {
            return error("Size too large");
        }
    }
    // Process data without bounds checking
    process_data(data, len);
}

Patched Code (Conceptual):

void unmarshal_spotlight_request(uint8_t *data, size_t len) {
    // Proper bounds check
    if (len > MAX_SPOTLIGHT_SIZE) {
        return error("Size too large");
    }
    // Process data with bounds checking
    process_data(data, len);
}

The fix would involve removing the dead code and placing the bounds check in the correct, reachable location.

Exploitation & Lab Setup

Red Team

Prerequisites:

• A Netatalk server running version 3.0.0 to 4.4.2 with Spotlight enabled.
• Valid credentials for an AFP user.

Exploitation Steps:

1. Identify Target: Scan for Netatalk servers on port 548 (AFP).
2. Authenticate: Use a valid AFP username and password to connect to the server.
3. Craft Payload: Create a Spotlight RPC request with an oversized or malformed data field. The exact structure depends on the Netatalk version and the specific dead bounds check.
4. Send Request: Send the crafted request to the server.
5. Extract Data: Analyze the response or server memory to extract leaked information.

Example Payload (Conceptual):

import socket

def exploit(host, port, username, password):
    # Establish AFP session (simplified)
    sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    sock.connect((host, port))
    # Perform AFP login (omitted for brevity)
    # Send crafted Spotlight RPC request
    payload = b"\x00" * 10000  # Oversized payload
    sock.send(payload)
    response = sock.recv(4096)
    print(response)
    sock.close()

Blue Team

Detection:

• Monitor for unusually large Spotlight RPC requests.
• Look for repeated failed authentication attempts followed by Spotlight RPC traffic.
• Use network intrusion detection systems to flag malformed AFP packets.

Hunting:

• Search for Netatalk processes with high memory usage or crashes.
• Review logs for errors related to Spotlight RPC unmarshalling.

Mitigation:

• Disable Spotlight functionality if not required.
• Restrict AFP access to trusted users and networks.
• Apply network segmentation to limit exposure.

Indicators of Compromise (IOCs)

• Network:
  • Unusually large AFP packets (size > 10KB) on port 548.
  • Malformed Spotlight RPC requests with invalid data lengths.
• Host:
  • Netatalk process crashes or segmentation faults.
  • Log entries containing "Spotlight RPC unmarshaller error" or similar.
  • Unexpected memory dumps or core files from the Netatalk process.
• File:
  • Temporary files created by Netatalk with unusual names or sizes.

Detection Engineering

YARA Rule

rule CVE_2026_44057_Netatalk_Spotlight_Dead_Bounds {
    meta:
        description = "Detects Netatalk versions vulnerable to CVE-2026-44057"
        author = "Valters IT"
        date = "2026-01-01"
        reference = "CVE-2026-44057"
    strings:
        $vuln_version_1 = "Netatalk 3.0" ascii
        $vuln_version_2 = "Netatalk 3.1" ascii
        $vuln_version_3 = "Netatalk 3.2" ascii
        $vuln_version_4 = "Netatalk 3.3" ascii
        $vuln_version_5 = "Netatalk 3.4" ascii
        $vuln_version_6 = "Netatalk 4.0" ascii
        $vuln_version_7 = "Netatalk 4.1" ascii
        $vuln_version_8 = "Netatalk 4.2" ascii
        $vuln_version_9 = "Netatalk 4.3" ascii
        $vuln_version_10 = "Netatalk 4.4" ascii
    condition:
        any of them
}

Sigma Rule

title: CVE-2026-44057 - Netatalk Spotlight RPC Dead Bounds Check
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects exploitation attempts of CVE-2026-44057 via oversized Spotlight RPC requests
author: Valters IT
date: 2026-01-01
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2026-44057
logsource:
    category: network
    product: netatalk
detection:
    selection:
        event: "Spotlight RPC request"
        size: "> 10000"
    condition: selection
falsepositives:
    - Legitimate large search queries
level: medium

Suricata Rule

alert tcp $EXTERNAL_NET any -> $HOME_NET 548 (msg:"CVE-2026-44057 - Netatalk Spotlight RPC Dead Bounds Check"; flow:to_server,established; content:"|00 00 00 00|"; depth:4; byte_test:4,>,10000,0; classtype:attempted-recon; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable Spotlight: If not required, disable the Spotlight feature in Netatalk configuration (spotlight = no in afp.conf).
2. Restrict Access: Use firewall rules to limit access to port 548 to trusted IP addresses only.
3. Monitor Logs: Enable detailed logging for Netatalk and monitor for suspicious activity.

Long-Term Fix:

• Patch: Await an official patch from the Netatalk project. Monitor the Netatalk GitHub repository and mailing list for updates.
• Upgrade: Once a patched version is released (e.g., 4.4.3 or later), upgrade immediately.
• Workaround: If patching is not possible, consider using an alternative file sharing protocol (e.g., SMB) until a fix is available.

Valters IT Signature

This report was generated by Valters IT DevSecOps AI Assistant. For questions, contact security@valters-it.com.