CVE-2026-87853
Sssd: sssd: idp authentication prefix comparison allows cross-user impersonation
What happened?
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 software and versions
| Software | Version information | Fixed version |
|---|---|---|
| sssdRed Hat | unaffected: 0:2.12.0-3.el10_2.2 to < * | See vendor advisory |
| sssdRed Hat | Default status: unknown | See vendor advisory |
| sssdRed Hat | Default status: unaffected | See vendor advisory |
| sssdRed Hat | Default status: unaffected | See vendor advisory |
| sssdRed Hat | Default status: unaffected | See vendor advisory |
| openshift/ose-rhel-coreos-8Red Hat | Default status: unaffected | See vendor advisory |
| openshift/ose-rhel-coreos-9Red Hat | Default status: unaffected | See vendor advisory |
| openshift/ose-rhel-coreos-9Red Hat | Default status: unaffected | See vendor advisory |
Version information comes from the source record and can include unaffected products and exceptions. Distribution packages may contain backported fixes: an older upstream version alone does not prove a server is affected.
Is it being exploited?
This CVE was not listed in the CISA catalogue at our last retrieval. This does not establish that exploitation is absent.
How to respond
- Confirm the product, installed package version, and any configuration requirements in the vendor advisory.
- Follow the vendor’s remediation or workaround guidance in the references below. Structured fixed-version data is unavailable here; the publisher’s description may include a fix or workaround.
- Restart affected services if required, then verify the running version. Known exploitation may warrant investigation as well as patching.