CVE-2026-87853
Sssd: sssd: idp authentication prefix comparison allows cross-user impersonation
- State
- Published
- Severity
- 7.5 High
- Published
- Sep 9, 2026
- Updated
- Oct 29, 2026
- Reserved
- 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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 3.1 | 7.5 High | CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H | redhat |
Weaknesses
- CWE-187 Partial String Comparison
Affected Products
| Product | Versions |
|---|---|
Red Hat Enterprise Linux 10Red Hat |
|
Red Hat Enterprise Linux 6Red Hat | |
Red Hat Enterprise Linux 7Red Hat | |
Red Hat Enterprise Linux 8Red Hat | |
Red Hat Enterprise Linux 9Red Hat | |
Red Hat OpenShift Container Platform 4Red Hat | |
Red Hat OpenShift Container Platform 4Red Hat |
References
- RHSA-2026:77534vendor-advisory
- https://access.redhat.com/security/cve/CVE-2026-87853vdb-entry
- RHBZ#2530888issue-tracking
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