CVE-2026-7835 Overview
CVE-2026-7835 is a format string vulnerability [CWE-134] affecting Netatalk versions 3.0.3 through 4.4.2. Netatalk is an open-source implementation of the Apple Filing Protocol (AFP) used to provide file services to macOS clients from Unix and Linux systems. The flaw stems from a mismatch between format string specifiers and the arguments passed during processing of crafted input. A remote authenticated attacker can trigger incorrect format string handling, resulting in a minor denial of service condition on the affected service.
Critical Impact
A remote authenticated attacker can cause a minor denial of service against Netatalk file services by submitting crafted input that triggers the format string mismatch.
Affected Products
- Netatalk 3.0.3 through 4.4.2
- Unix and Linux hosts running vulnerable Netatalk AFP services
- Network-attached storage (NAS) appliances bundling affected Netatalk versions
Discovery Timeline
- 2026-05-21 - CVE CVE-2026-7835 published to NVD
- 2026-05-21 - Last updated in NVD database
Technical Details for CVE-2026-7835
Vulnerability Analysis
The vulnerability is classified under [CWE-134] Use of Externally-Controlled Format String. Netatalk processes input where format string specifiers do not align with the arguments supplied to the underlying formatting function. When the function processes the mismatched specifier, it reads from unintended stack or register locations and produces undefined behavior. In this case the behavior manifests as a service-level fault rather than memory disclosure or code execution.
The attack requires valid authentication to the AFP service. The attacker must reach the network-exposed Netatalk daemon and submit crafted protocol input that hits the affected code path. The CVSS vector indicates high attack complexity, network reach, low privileges required, no user interaction, and limited availability impact only. Confidentiality and integrity are not affected.
Root Cause
The root cause is an argument-count or type mismatch between a format string and the variadic arguments passed alongside it in Netatalk's input processing code. When the formatting routine walks the format string, it consumes arguments that were never provided in the expected layout, producing inconsistent state that disrupts the request handler.
Attack Vector
An authenticated remote user connects to the Netatalk AFP service over the network and submits specially crafted protocol input. The crafted payload reaches the vulnerable formatting code path and triggers the mismatch. The result is a localized denial of service against the request or session. No verified public proof-of-concept exploit is available, and the vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog.
No verified exploitation code is available. Refer to the Netatalk Security Advisory CVE-2026-7835 for technical details published by the project maintainers.
Detection Methods for CVE-2026-7835
Indicators of Compromise
- Unexpected crashes, restarts, or hangs of the afpd or netatalk daemon processes.
- AFP session terminations correlated with authenticated client activity from a single source.
- Error or assertion entries in Netatalk logs immediately following malformed protocol requests.
Detection Strategies
- Monitor process supervision logs (systemd, launchd, or init scripts) for repeated Netatalk service restarts.
- Inspect Netatalk logs at /var/log/netatalk.log for format string warnings, abnormal request entries, or session aborts.
- Correlate authenticated AFP sessions with subsequent daemon failures to identify abusive accounts.
Monitoring Recommendations
- Track AFP service uptime and crash counts through host monitoring tooling.
- Alert on authentication events from accounts that precede service faults.
- Capture network traffic to the AFP port (TCP 548) for forensic review when daemon failures occur.
How to Mitigate CVE-2026-7835
Immediate Actions Required
- Inventory all hosts and NAS appliances running Netatalk versions 3.0.3 through 4.4.2.
- Upgrade Netatalk to a fixed release as published in the Netatalk Security Advisory CVE-2026-7835.
- Restrict AFP service exposure to trusted network segments using host or network firewalls.
- Review AFP account inventory and remove unused or shared credentials to limit authenticated attack surface.
Patch Information
The Netatalk project documents fixed versions and remediation guidance in the Netatalk Security Advisory CVE-2026-7835. Administrators should apply the vendor-supplied update for their distribution or rebuild from upstream sources at the patched release.
Workarounds
- Disable the Netatalk service on hosts that do not require AFP file sharing.
- Block inbound connections to TCP port 548 from untrusted networks at the perimeter firewall.
- Limit AFP authentication to a small set of known accounts and rotate credentials of any accounts suspected of abuse.
# Configuration example: restrict AFP access at the host firewall
# Allow AFP only from a trusted management subnet
iptables -A INPUT -p tcp --dport 548 -s 10.0.10.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 548 -j DROP
# Verify installed Netatalk version
afpd -V
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
