High severity · published Sep 9, 2026
CVE-2026-87853
Sssd: sssd: idp authentication prefix comparison allows cross-user impersonation
7.5
CVSS
0.3%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Attack vector
Network
Complexity
High
Privileges
Low
User interaction
None
Confidentiality
High
Integrity
High
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.3% · higher than 26% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
RH
Red Hat Enterprise Linux 10 · Red Hat
All versions, or not specified · source: vendor
RH
Red Hat Enterprise Linux 6 · Red Hat
All versions, or not specified · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-87853
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-87853
vendor-advisory
https://access.redhat.com/errata/RHSA-2026:77534
vdb-entry
https://access.redhat.com/security/cve/CVE-2026-87853
issue-tracking
https://bugzilla.redhat.com/show_bug.cgi?id=2530888
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