# CVE-2026-87853

## Summary

- **CVE ID:** CVE-2026-87853
- **Severity:** HIGH
- **CVSS Score:** 7.5 (CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H)
- **CWE:** CWE-187
- **Published:** Sep 9, 2026
- **Last Modified:** Sep 9, 2026

## Description

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.

## Affected Products

No affected products listed.

## References

- [CNA](https://access.redhat.com/security/cve/CVE-2026-87853)
- [CNA](https://bugzilla.redhat.com/show_bug.cgi?id=2530888)

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-09._