Executive Summary

A vulnerability in the seekdir() function of relibc, a C standard library for Redox OS, allows attackers to cause a Denial of Service (DoS) via a crafted input. This vulnerability is classified as HIGH severity with a CVSS score of 7.5. Currently, there is no evidence of active exploitation.

Technical Analysis

The vulnerability is located in the seekdir() function in the /dirent/mod.rs file of relibc at commit 61f42d. The vulnerability class is CWE-400, which refers to an Uncontrolled Resource Consumption issue. An attacker can trigger this flaw by providing a crafted input to the seekdir() function, which can cause the system to consume excessive resources, leading to a Denial of Service (DoS).

How It Gets Exploited

An attacker can exploit this vulnerability by sending a crafted input to the seekdir() function. The attacker's starting position would likely be an unauthenticated remote attacker on the same network or a low-privileged user with access to the system. The specific action that triggers the vulnerability involves providing a specially crafted input that causes the seekdir() function to consume excessive resources. When the flaw is triggered, the system fails to handle the input properly, leading to a resource consumption issue that results in a Denial of Service (DoS). The attacker gains the ability to disrupt the system's availability.

Impact Assessment

The vulnerability affects relibc at commit 61f42d. An attacker can achieve a Denial of Service (DoS) with this vulnerability, impacting the availability of the system. The CVSS score of 7.5 indicates a HIGH severity level, with the attack vector being NETWORK, attack complexity being LOW, and availability impact being HIGH.

Recommended Actions

To mitigate this vulnerability, it is recommended to update relibc to a version that includes the fix for this issue. Specifically, apply the merge request https://gitlab.redox-os.org/redox-os/relibc/-/merge_requests/980. Additionally, users can consider implementing network segmentation or access controls to limit the attack surface. Monitoring system resources and implementing detection mechanisms for unusual resource consumption patterns can also help identify potential exploitation attempts.

Sources

  • National Vulnerability Database (NVD) - https://nvd.nist.gov/vuln/detail/CVE-2026-38636
  • GitHub PoC - https://github.com/Marsman1996/pocs/tree/master/redox/CVE-2026-38636
  • Redox OS relibc Issue - https://gitlab.redox-os.org/redox-os/relibc/-/issues/260
  • Redox OS relibc Merge Request - https://gitlab.redox-os.org/redox-os/relibc/-/merge_requests/980