CVE-2026-22213: RIOT OS Buffer Overflow Vulnerability

CVE-2026-22213 Overview

RIOT OS versions up to and including 2026.01-devel-317 contain a stack-based buffer overflow vulnerability in the tapslip6 utility. The vulnerability is caused by unsafe string concatenation in the devopen() function, which constructs a device path using unbounded user-controlled input. The utility uses strcpy() and strcat() to concatenate the fixed prefix /dev/ with a user-supplied device name provided via the -s command-line option without bounds checking. This allows an attacker to supply an excessively long device name and overflow a fixed-size stack buffer, leading to process crashes and memory corruption.

Critical Impact

Local attackers with user privileges can cause denial of service through stack buffer overflow by providing an excessively long device name to the tapslip6 utility.

Affected Products

• RIOT OS versions up to and including 2026.01-devel-317
• Systems running the tapslip6 utility
• IoT deployments utilizing RIOT OS network utilities

Discovery Timeline

• January 12, 2026 - CVE-2026-22213 published to NVD
• January 13, 2026 - Last updated in NVD database

Technical Details for CVE-2026-22213

Vulnerability Analysis

This vulnerability falls under CWE-121 (Stack-based Buffer Overflow), a classic memory corruption flaw common in C/C++ applications that use unsafe string manipulation functions. The tapslip6 utility is a networking tool within RIOT OS used for serial line IP connectivity on embedded and IoT devices.

The vulnerability requires local access to the system where RIOT OS is installed, and user interaction is necessary to trigger exploitation since the malicious input must be provided via command-line arguments. The primary impact is availability degradation through process crashes, as successful exploitation corrupts the stack and terminates the affected process.

Root Cause

The root cause of this vulnerability is the use of unsafe C standard library functions strcpy() and strcat() without proper bounds checking. The devopen() function allocates a fixed-size buffer on the stack to construct the full device path by concatenating /dev/ with the user-supplied device name from the -s command-line option. Because no length validation is performed on the input before concatenation, an attacker can supply a device name that exceeds the buffer's capacity, causing a stack buffer overflow.

This is a fundamental secure coding issue where bounded alternatives like strncpy() or strlcat() should be used, or proper input validation should be implemented to restrict the length of user-supplied data.

Attack Vector

The attack vector is local, requiring the attacker to have access to a system running RIOT OS with the vulnerable tapslip6 utility. The attacker must execute the tapslip6 command with the -s option followed by an excessively long device name string. When the devopen() function attempts to construct the device path, the oversized input overflows the stack buffer.

The exploitation mechanism involves providing a crafted string that exceeds the expected buffer size. When processed by strcpy() and strcat(), the overflow corrupts adjacent stack memory, potentially overwriting the return address or other critical stack data, resulting in a crash or undefined behavior.

For technical exploitation details, refer to the Full Disclosure Security Mailing List and the VulnCheck Advisory.

Detection Methods for CVE-2026-22213

Indicators of Compromise

• Unexpected crashes or segmentation faults involving the tapslip6 process
• Core dumps with stack corruption signatures in the devopen() function
• System logs showing tapslip6 invocations with unusually long command-line arguments

Detection Strategies

• Monitor system calls and command-line arguments for tapslip6 executions with oversized -s parameters
• Implement process monitoring to detect abnormal terminations of network utilities
• Deploy static analysis tools to identify usage of unsafe string functions in RIOT OS deployments

Monitoring Recommendations

• Enable core dump collection and analysis for embedded systems running RIOT OS
• Configure logging for all tapslip6 utility invocations with full argument capture
• Implement file integrity monitoring on RIOT OS binaries to detect unauthorized modifications

How to Mitigate CVE-2026-22213

Immediate Actions Required

• Restrict access to the tapslip6 utility to trusted administrators only
• Audit systems for RIOT OS versions up to and including 2026.01-devel-317
• Consider removing or disabling the tapslip6 utility if not required for operations
• Apply input validation wrappers around the utility if it must remain in use

Patch Information

Users should monitor the RIOT OS GitHub Repository for updates that address this vulnerability. Check the VulnCheck Advisory for the latest patch status and remediation guidance. Review the RIOT OS Official Website for security announcements.

Workarounds

• Create wrapper scripts that validate the length of the -s argument before passing to tapslip6
• Limit execution permissions on the tapslip6 binary to prevent unauthorized use
• Use application sandboxing or containerization to isolate the utility from critical system components
• Consider recompiling tapslip6 with stack protection mechanisms (e.g., -fstack-protector-strong)

# Example: Restrict tapslip6 execution permissions
chmod 750 /path/to/tapslip6
chown root:trusted_group /path/to/tapslip6