A critical stack buffer overflow in the rxi microtar library allows for potential remote code execution when processing maliciously crafted filenames.

The functions mtar_write_file_header and mtar_write_dir_header perform a strcpy operation into a fixed-size 100-byte stack buffer without verifying the input length. This allows an attacker to supply a filename exceeding 99 characters, triggering an overflow that can be exploited by unauthenticated remote attackers.

Successful exploitation of this buffer overflow could lead to arbitrary code execution, allowing an attacker to gain control over the host process. Given the 9.8 CVSS score, this represents a major threat to system integrity and availability, particularly for applications that handle untrusted archives or user-provided filenames.

Immediate Action: Review applications utilizing the microtar library to ensure all input filenames are strictly validated for length before being passed to library functions.

Proactive Monitoring: Monitor for application crashes or segmentation faults that may indicate an attempt to exploit memory corruption vulnerabilities.

Compensating Controls: Compile the application with modern memory safety protections, such as stack canaries and Address Space Layout Randomization (ASLR), to increase the difficulty of successful exploitation.

Public Exploit Available: Unknown

Developers should immediately audit their use of the microtar library and implement mandatory length checks for all filenames. Until a formal library update is available, manual input sanitization is the most effective way to mitigate this critical risk.