---
id: "CVE-2026-127101"
page: "https://infrastack.ai/live/CVE-2026-127101"
kind: "vulnerability"
aliases: ["CVE-2026-127101"]
title: "SSSD: crafted PAM request crashes authentication responder, denying logins"
severity: "medium"
cvss: 5.5
epss: null
exploited: false
status: "open"
category: "infrastructure"
products: []
ecosystems: []
tags: ["infrastructure", "linux", "pam", "self-hosted", "sssd"]
not_affected_if: ["no-local-access", "no-sssd"]
published_at: "2026-11-12T18:17:41+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-2026-127101", "first_seen_at": "2026-11-12T18:40:39+00:00"}]
exploit_sources: []
---

# SSSD: crafted PAM request crashes authentication responder, denying logins

Link for people: https://infrastack.ai/live/CVE-2026-127101 (this .md is for agents)

SSSD's PAM responder dereferences a NULL protocol-version pointer when an authentication request arrives before the client protocol version is negotiated. A local attacker can crash the responder and, by repeating crafted requests, keep SSSD-backed authentication down.

_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`
- Confirm whether PAM authentication goes through SSSD by looking for `sss` in `/etc/nsswitch.conf` and `pam_sss` in `/etc/pam.d/`

## Timeline

- 2026-11-12T18:40:39+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-127101

## From the sources

A flaw was found in SSSD's PAM responder. A local attacker can send an authentication request without first negotiating the client protocol version. The responder dereferences a NULL protocol-version pointer and crashes, disrupting SSSD-backed authentication. Repeated crafted requests can sustain the denial of service.

---

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