CVE-2026-38641 Overview
CVE-2026-38641 is a denial of service vulnerability in relibc, the C standard library implementation used by the Redox operating system. The flaw resides in the DSO::mmap_and_copy function at commit 61f42d. An attacker who supplies a crafted shared library can trigger the issue during dynamic loading, causing the process to terminate or hang. The vulnerability is tracked under CWE-404: Improper Resource Shutdown or Release.
Critical Impact
A crafted shared library loaded through relibc causes availability loss in any process that depends on the dynamic loader.
Affected Products
- Redox OS relibc at commit 61f42d
- Applications on Redox OS that link against the affected relibc build
- Dynamic loader components exercising DSO::mmap_and_copy
Discovery Timeline
- 2026-06-26 - CVE-2026-38641 published to NVD
- 2026-06-29 - Last updated in NVD database
Technical Details for CVE-2026-38641
Vulnerability Analysis
The vulnerability lives inside the DSO::mmap_and_copy function of relibc, the Redox OS C standard library. This function maps segments of a dynamic shared object (DSO) into memory and copies program data during shared library loading. When the loader parses a maliciously crafted shared library, the function fails to handle malformed segment metadata correctly. The result is improper resource shutdown or release, categorized as [CWE-404], which terminates the loading process and denies service to any application depending on the library.
Because the flaw is exercised during dynamic loading, exploitation does not require successful execution of attacker code. Simply attempting to load the object is sufficient to disrupt availability. Confidentiality and integrity are not affected, but availability impact is high.
Root Cause
The root cause is improper handling of memory mapping and copy operations for DSO segments. When segment headers describe invalid sizes, offsets, or alignment values, DSO::mmap_and_copy does not gracefully release the partially acquired mapping resources. This leads to a fatal condition that aborts the loader.
Attack Vector
An attacker delivers a crafted shared library to a target that will load it through relibc's dynamic loader. Delivery can occur over the network if a service accepts shared object files, plugins, or module archives. Once loading is attempted, the affected process becomes unavailable. See the GitLab issue report and the GitHub PoC repository for technical details and reproduction steps.
Detection Methods for CVE-2026-38641
Indicators of Compromise
- Unexpected termination or crashes of processes invoking the Redox relibc dynamic loader
- Presence of unfamiliar .so files in application plugin or library directories
- Repeated process restarts correlated with shared library load attempts
Detection Strategies
- Monitor process exit codes and crash logs for processes linked against affected relibc builds
- Inspect shared library files loaded at runtime against a known-good allowlist
- Review file transfer and upload logs for unexpected shared object uploads to servers running Redox OS
Monitoring Recommendations
- Enable auditing of mmap and dynamic loader activity in Redox OS environments
- Alert on repeated abnormal termination of services that dynamically load third-party modules
- Track integrity of directories containing plugins or extensions consumed by Redox-based applications
How to Mitigate CVE-2026-38641
Immediate Actions Required
- Update relibc to a build that includes the fix delivered through merge request 1046
- Restrict which users and processes can supply shared libraries to Redox OS services
- Disable or restrict plugin loading in applications that accept untrusted shared objects
Patch Information
The Redox project addressed the issue in relibc through GitLab merge request 1046, which corrects the resource handling in DSO::mmap_and_copy. Rebuild and redeploy relibc and any dependent binaries after applying the patched revision. Confirm remediation by re-running the reproducer from the public PoC repository.
Workarounds
- Block untrusted shared object uploads at the network perimeter
- Run affected services under process supervisors that isolate crashes and prevent cascading failures
- Apply filesystem permissions that prevent non-privileged users from writing to loader search paths
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
