# CVE-2026-38637: Redox OS relibc Denial of Service in pthread_rwlockattr_setpshared

Source: https://junglewise.ai/threats/cve-2026-38637-redox-os-relibc-denial-of-service-in-pthread-rwlockattr  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-06-25. Updated: 2026-06-25  
License: CC BY 4.0 with a link back

CVE-2026-38637 · Severity: info · CVSS 4 · Published 2026-06-25

A vulnerability exists in relibc, a core C library used by the Redox operating system. An attacker can cause a program to crash by providing unexpected input to a specific system function. This results in a denial-of-service condition where the affected application stops functioning, potentially impacting system stability or service availability.

Technologies: [Redox OS Relibc](https://junglewise.ai/threats/technologies/relibc). Vendors: [Redox OS](https://junglewise.ai/threats/vendors/redox-os).

## Quick answers

**Is CVE-2026-38637 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-38637 being exploited in the wild.

**How severe is CVE-2026-38637?** Informational severity, with a CVSS score of 4, published 25 June 2026.

**Which products and versions are affected?** Redox OS Relibc commit 61f42d6b93adc552a9e8b6f207fca907e8ca8be2.

**Is there a fix for CVE-2026-38637?** A patch was published on 2026-02-10: Merge request !987 submitted to handle invalid pshared values. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-38637 attacked?** It is attacked with local access, in a software library.

**Am I affected by CVE-2026-38637?** Check whether you run Redox OS Relibc at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A reachable 'expect' panic exists in the pthread_rwlockattr_setpshared() function within relibc (specifically in src/header/pthread/rwlock.rs). The root cause is the use of .expect() on a Result/Option returned by Pshared::from_raw() when an invalid pshared value (neither PTHREAD_PROCESS_PRIVATE nor PTHREAD_PROCESS_SHARED) is provided. A local attacker can trigger this panic by executing a program that passes an unsupported integer to the function, leading to an immediate process crash (SIGILL/Invalid Opcode). A fix has been proposed in merge request !987 to return EINVAL instead of panicking.

## Affected products

- Redox OS relibc commit 61f42d6b93adc552a9e8b6f207fca907e8ca8be2

## Timeline

- 2026-02-10: patched: Merge request !987 submitted to handle invalid pshared values.
- 2026-06-25: disclosed: CVE-2026-38637 published.

## References

- [https://github.com/Marsman1996/pocs/tree/master/redox/CVE-2026-38637](https://github.com/Marsman1996/pocs/tree/master/redox/CVE-2026-38637)
- [https://gitlab.redox-os.org/redox-os/relibc/-/issues/264](https://gitlab.redox-os.org/redox-os/relibc/-/issues/264)
- [https://gitlab.redox-os.org/redox-os/relibc/-/merge_requests/987](https://gitlab.redox-os.org/redox-os/relibc/-/merge_requests/987)
- [https://gitlab.redox-os.org/redox-os/relibc/-/work_items/264](https://gitlab.redox-os.org/redox-os/relibc/-/work_items/264)

## Related threats

- [relibc index out of bounds in with_argv](https://junglewise.ai/threats/cve-2026-38638-relibc-index-out-of-bounds-in-with-argv)
- [relibc seekdir() denial of service via invalid offset](https://junglewise.ai/threats/cve-2026-38636-relibc-seekdir-denial-of-service-via-invalid-offset)
- [Redox OS relibc denial of service in DSO::mmap_and_copy](https://junglewise.ai/threats/cve-2026-38641-redox-os-relibc-denial-of-service-in-dso-mmap-and-copy)
- [Redox OS relibc Denial of Service in strptime via multibyte characters](https://junglewise.ai/threats/cve-2026-38639-redox-os-relibc-denial-of-service-in-strptime-via-multibyte)
- [Redox OS relibc Denial of Service in __assert_fail](https://junglewise.ai/threats/cve-2026-38640-redox-os-relibc-denial-of-service-in-assert-fail)