---
id: CVE-2026-87853
title: A flaw was found in SSSD's IdP authentication provider
summary: >-
  A flaw was found in SSSD's IdP authentication provider. The
  eval_access_token_buf() function compares the OIDC subject identifier using
  strncmp() with the authenticated user's identifier length, performing a prefix
  comparison instead of …
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H'
cwe:
  - CWE-187
vendor: Red Hat
product: sssd
affected:
  - sssd (all versions)
  - sssd
  - sssd
  - sssd
  - sssd
  - openshift/ose-rhel-coreos-8
  - openshift/ose-rhel-coreos-9
published: '2026-09-09'
updated: '2026-09-10'
sourceUpdated: '2026-09-10T15:17:54.240'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-87853'
references:
  - url: 'https://access.redhat.com/security/cve/CVE-2026-87853'
    label: secalert@redhat.com
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2530888'
    label: secalert@redhat.com
tags:
  - nvd
  - cve.org
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: total
  timestamp: '2026-09-09T18:28:46.606582Z'
ingestedAt: '2026-09-13T05:23:50.971Z'
epss: 0.00477
epssPercentile: 0.38609
---

## Overview

A flaw was found in SSSD's IdP authentication provider. The eval_access_token_buf() function compares the OIDC subject identifier using strncmp() with the authenticated user's identifier length, performing a prefix comparison instead of an exact match. An attacker whose IdP identifier is a strict prefix of a target user's identifier can authenticate as the target user.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.