# CVE-2026-127099: SSSD stack buffer overflow in X.509 RSA certificate conversion

Source: https://junglewise.ai/threats/cve-2026-127099-a-flaw-was-found-in-sssd-s-conversion-of-x-509-certificate-rsa  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-11-12. Updated: 2026-11-12  
License: CC BY 4.0 with a link back

CVE-2026-127099 · Severity: medium · CVSS 5.9 · Published 2026-11-12

SSSD is a system daemon that manages user authentication and authorization across Linux systems. The vulnerability allows an attacker with the ability to supply a specially crafted certificate to trigger a denial-of-service condition or corrupt SSH authentication memory. Exploitation requires the attacker to pass the system's certificate validation checks and have low-level access to certificate attributes.

Technologies: [Red Hat SSSD](https://junglewise.ai/threats/technologies/red-hat-sssd). Vendors: [Red Hat](https://junglewise.ai/threats/vendors/red-hat).

## Quick answers

**Is CVE-2026-127099 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-127099 being exploited in the wild.

**How severe is CVE-2026-127099?** Medium severity, with a CVSS score of 5.9, published 12 November 2026.

**Which products and versions are affected?** Red Hat SSSD.

**Is there a fix for CVE-2026-127099?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-127099 attacked?** It is attacked over the network, in a hosted service.

**Am I affected by CVE-2026-127099?** Check whether you run Red Hat SSSD. 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 stack buffer overflow exists in SSSD's conversion of X.509 certificate RSA public keys to SSH keys due to missing size validation before copying RSA components into fixed-size buffers. The vulnerability is reachable via network through certificate-based SSH key lookup; exploitation requires an attacker-controlled certificate passing configured validation checks and low-privileged certificate attribute write access. Successful exploitation causes SSH responder denial of service and memory corruption, though arbitrary code execution has not been demonstrated.

## Affected products

- Red Hat SSSD

## Timeline

- 2026-11-12: disclosed

## References

- [https://access.redhat.com/downloads/content/package-browser/](https://access.redhat.com/downloads/content/package-browser/)
- [https://access.redhat.com/security/cve/CVE-2026-127099](https://access.redhat.com/security/cve/CVE-2026-127099)

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