CVE-2026-44050: Netatalk CNID Daemon RCE Vulnerability

CVE-2026-44050 Overview

CVE-2026-44050 is a heap-based buffer overflow [CWE-122] in the comm_rcv() function of the Concurrent Network Identifier Database (CNID) daemon shipped with Netatalk. The flaw affects Netatalk versions 2.0.0 through 4.4.2. A remote authenticated attacker can exploit the overflow to execute arbitrary code with escalated privileges or trigger a denial of service. Netatalk implements the Apple Filing Protocol (AFP) and is widely deployed on Linux and BSD file servers that provide network shares to macOS clients.

Critical Impact

Authenticated network attackers can corrupt heap memory inside the CNID daemon to gain code execution with daemon privileges or crash the file service.

Affected Products

• Netatalk 2.0.0 through 2.x
• Netatalk 3.0.0 through 3.x
• Netatalk 4.0.0 through 4.4.2

Discovery Timeline

• 2026-05-21 - CVE-2026-44050 published to the National Vulnerability Database
• 2026-05-21 - Last updated in NVD database

Technical Details for CVE-2026-44050

Vulnerability Analysis

The vulnerability resides in the comm_rcv() function of the CNID daemon (cnid_dbd). This daemon maintains persistent file identifier mappings used by the AFP server (afpd) when serving macOS clients. The comm_rcv() routine reads request messages from connected afpd workers over a local communication channel and parses length-prefixed fields into a fixed heap buffer.

When the daemon processes an attacker-influenced message whose declared length exceeds the destination buffer, the copy operation writes past the allocated region. Adjacent heap metadata and neighboring chunks can be overwritten. The vulnerability is reachable across the network because authenticated AFP clients can drive the afpd worker into issuing crafted CNID requests on their behalf.

Root Cause

The root cause is missing or insufficient bounds validation between the message length supplied on the wire and the size of the destination heap allocation inside comm_rcv(). The function trusts attacker-controllable length data when copying payload bytes, which is the classic [CWE-122] heap-based buffer overflow pattern.

Attack Vector

Exploitation requires valid AFP credentials on the target Netatalk server. After authentication, the attacker issues AFP operations that cause afpd to forward a malformed CNID request to cnid_dbd. The malformed request triggers the overflow inside the daemon process. Because cnid_dbd typically runs with elevated privileges to manage the shared CNID database, successful memory corruption can yield code execution outside the scope of the authenticated user, satisfying the scope-changed condition reflected in the CVSS vector.

No verified public proof-of-concept has been released. See the Netatalk Security Advisory for vendor-supplied technical details.

Detection Methods for CVE-2026-44050

Indicators of Compromise

• Unexpected crashes, restarts, or SIGSEGV signals from the cnid_dbd or cnid_metad processes recorded in system logs.
• Child processes spawned by cnid_dbd or afpd that do not match the standard Netatalk process tree, such as shells or network utilities.
• Outbound network connections originating from the Netatalk service account immediately after AFP authentication events.
• Modifications to CNID database files (cnid2.db, *.db) outside of normal file service activity.

Detection Strategies

• Monitor for AFP authentication events followed by abnormal CNID daemon termination within a short time window.
• Alert on process executions where the parent is cnid_dbd, cnid_metad, or afpd and the child is an interpreter, shell, or networking binary.
• Inspect core dumps from Netatalk daemons for heap corruption signatures consistent with overwritten chunk metadata.

Monitoring Recommendations

• Enable verbose logging for afpd and cnid_dbd and forward logs to a centralized log platform for correlation.
• Track Netatalk package versions across the fleet and flag any host running a version at or below 4.4.2.
• Baseline normal CNID daemon memory usage and alert on sudden growth or repeated restarts.

How to Mitigate CVE-2026-44050

Immediate Actions Required

• Upgrade Netatalk to a fixed release published by the project as referenced in the Netatalk Security Advisory.
• Restrict AFP access at the network layer so that only trusted client subnets can reach TCP port 548.
• Audit AFP user accounts and disable or rotate credentials for any account that is unused, shared, or weakly authenticated.
• Enable address space layout randomization (ASLR) and position-independent executables for the Netatalk binaries on the host operating system.

Patch Information

The Netatalk project tracks the fix under the advisory at netatalk.io/security/CVE-2026-44050. Administrators should apply the vendor-supplied package update for Netatalk versions newer than 4.4.2, or backported security packages provided by their Linux or BSD distribution.

Workarounds

• Disable the Netatalk service on hosts that do not require AFP file sharing until a patched build is installed.
• Block inbound AFP traffic (TCP 548) at the perimeter and host firewall, allowing only required management subnets.
• Require strong authentication and enforce account lockout policies to raise the cost of obtaining the credentials needed to reach comm_rcv().

# Example: restrict AFP access with iptables and stop the service pending patch
sudo iptables -A INPUT -p tcp --dport 548 -s 10.0.0.0/24 -j ACCEPT
sudo iptables -A INPUT -p tcp --dport 548 -j DROP
sudo systemctl stop netatalk
sudo systemctl disable netatalk