Cross-user impersonation via partial subject comparison
Published Sep 9, 2026 · Updated Sep 10, 2026
Authentication bypass in SSSD on Red Hat Enterprise Linux 10.2 allows remote authenticated users to impersonate another OS user. The eval_access_token_buf() function passes the authenticated user identifier length to strncmp(), so a strict-prefix OIDC subject is accepted as an exact match. Exploitation requires the non-default SSSD IdP provider with Keycloak LDAP federation configured not to import users; an ordinary IdP account can then obtain the target user’s operating-system access.
Summary
What happened
Authentication bypass in SSSD on Red Hat Enterprise Linux 10.2 allows remote authenticated users to impersonate another OS user. The eval_access_token_buf() function passes the authenticated user identifier length to strncmp(), so a strict-prefix OIDC subject is accepted as an exact match. Exploitation requires the non-default SSSD IdP provider with Keycloak LDAP federation configured not to import users; an ordinary IdP account can then obtain the target user’s operating-system access.
The record
- CVE
- CVE-2026-87853
- Published
- Sep 9, 2026
- Updated
- Sep 10, 2026
- Vendor
- 389 Directory Server
- Product
- Red Hat Enterprise Linux 10
- Classifications
- CWE-187, T1078
- Attack vector
- network
- Privileges
- authenticated
Timeline
How it unfolded
- Sep 9, 2026CVE publishedPublication date reported by the CVE source.
- Sep 10, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
Compare your product and version with the public record. A matching version still requires validation against your environment.
Is a vulnerable build present?
Affected versions are unavailable in this record. Check the vendor advisory for version and patch details.
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Public exploit references
No public exploit references are available in this record.
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
See the directory against your own environment.
Your stack
Check the software in your environment
Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.
Book a demo