---
id: "CVE-2026-127099"
page: "https://infrastack.ai/live/CVE-2026-127099"
kind: "vulnerability"
aliases: ["CVE-2026-127099"]
title: "SSSD: oversized RSA key in certificate can overflow stack buffer"
severity: "medium"
cvss: 5.9
epss: null
exploited: false
status: "open"
category: "infrastructure"
products: []
ecosystems: []
tags: ["infrastructure", "linux", "self-hosted", "ssh", "sssd"]
not_affected_if: ["no-certificate-auth", "no-ssh-responder"]
published_at: "2026-11-12T18:17:40+00:00"
first_seen_at: "2026-11-12T18:40:39+00:00"
updated_at: "2026-11-12T18:42:58+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-127099", "first_seen_at": "2026-11-12T18:40:39+00:00"}]
exploit_sources: []
---

# SSSD: oversized RSA key in certificate can overflow stack buffer

Link for people: https://infrastack.ai/live/CVE-2026-127099 (this .md is for agents)

SSSD, the System Security Services Daemon, does not check RSA component sizes before copying them into fixed-size stack buffers when converting X.509 certificate keys to SSH keys. An attacker who can supply a certificate with oversized RSA components that passes the configured checks can crash the service and corrupt SSH responder memory.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check the installed SSSD version with `sssd --version` (or `rpm -q sssd` / `dpkg -l sssd`).
- Check whether the SSH responder is enabled in `/etc/sssd/sssd.conf` (the `ssh` service in `services`).
- Check whether certificate-based authentication is configured for SSSD.

## Timeline

- 2026-11-12T18:40:39+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-127099

## From the sources

A flaw was found in SSSD's conversion of X.509 certificate RSA public keys to SSH keys. Missing size checks before copying RSA components into fixed-size stack buffers can cause a stack buffer overflow. An attacker able to supply a certificate with oversized RSA components that passes the configured certificate checks can cause denial of service and corrupt SSH responder memory.

---

_Free to read, with fair use of about 60 pages a minute. For higher limits or API access: sales@infrastack.ai_