{"affected":[{"defaultStatus":"affected","ecosystem":"https://access.redhat.com/downloads/content/package-browser/","packageName":"sssd","product":"Red Hat Enterprise Linux 10","source":"CNA: redhat","vendor":"Red Hat","versions":[{"lessThan":"*","status":"unaffected","version":"0:2.12.0-3.el10_2.2","versionType":"rpm"}]},{"defaultStatus":"unknown","ecosystem":"https://access.redhat.com/downloads/content/package-browser/","packageName":"sssd","product":"Red Hat Enterprise Linux 6","source":"CNA: redhat","vendor":"Red Hat","versions":[]},{"defaultStatus":"unaffected","ecosystem":"https://access.redhat.com/downloads/content/package-browser/","packageName":"sssd","product":"Red Hat Enterprise Linux 7","source":"CNA: redhat","vendor":"Red Hat","versions":[]},{"defaultStatus":"unaffected","ecosystem":"https://access.redhat.com/downloads/content/package-browser/","packageName":"sssd","product":"Red Hat Enterprise Linux 8","source":"CNA: redhat","vendor":"Red Hat","versions":[]},{"defaultStatus":"unaffected","ecosystem":"https://access.redhat.com/downloads/content/package-browser/","packageName":"sssd","product":"Red Hat Enterprise Linux 9","source":"CNA: redhat","vendor":"Red Hat","versions":[]},{"defaultStatus":"unaffected","ecosystem":"https://access.redhat.com/downloads/content/package-browser/","packageName":"openshift/ose-rhel-coreos-8","product":"Red Hat OpenShift Container Platform 4","source":"CNA: redhat","vendor":"Red Hat","versions":[]},{"defaultStatus":"unaffected","ecosystem":"https://access.redhat.com/downloads/content/package-browser/","packageName":"openshift/ose-rhel-coreos-9","product":"Red Hat OpenShift Container Platform 4","source":"CNA: redhat","vendor":"Red Hat","versions":[]},{"defaultStatus":"unaffected","ecosystem":"https://access.redhat.com/downloads/content/package-browser/","packageName":"openshift/ose-rhel-coreos-9","product":"Red Hat OpenShift Container Platform 5","source":"CNA: redhat","vendor":"Red Hat","versions":[]}],"cveId":"CVE-2026-87853","cwes":["CWE-187"],"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.","epss":{"date":"2026-11-02","percentile":0.25889,"score":0.00328},"exploits":[],"kev":null,"metrics":[{"score":7.5,"severity":"high","source":"CNA: redhat","vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H","version":"3.1"}],"modifiedAt":1793685902194,"publishedAt":1788969985638,"references":[{"source":"CNA: redhat","tags":["vendor-advisory","x_refsource_REDHAT"],"url":"https://access.redhat.com/errata/RHSA-2026:77534"},{"source":"CNA: redhat","tags":["vdb-entry","x_refsource_REDHAT"],"url":"https://access.redhat.com/security/cve/CVE-2026-87853"},{"source":"CNA: redhat","tags":["issue-tracking","x_refsource_REDHAT"],"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2530888"}],"remediation":[{"kind":"workaround","source":"CNA: redhat","text":"Deployments not using the IdP authentication provider (idp_type = keycloak) are not affected. For affected deployments: (1) If using Keycloak LDAP federation, switching to Import Users: enabled mode causes Keycloak to assign random UUIDs as sub claims, making prefix collisions astronomically unlikely. (2) Restrict PAM login to specific users via simple_allow_users or access_provider = simple. (3) Disable Keycloak self-registration to prevent attackers from creating accounts with chosen prefix usernames."}],"revision":"446869b2c6c8643b4c5b1bcda640c15f442c2e1224a12100fd6d948c28332939","sources":[{"modifiedAt":1793685902194,"name":"CNA: redhat","retrievedAt":1793689782521,"url":"https://www.cve.org/CVERecord?id=CVE-2026-87853"},{"modifiedAt":null,"name":"FIRST EPSS","retrievedAt":1793689784422,"url":"https://api.first.org/data/v1/epss?cve=CVE-2026-87853"}],"ssvc":{"assessedAt":1788978526606,"automatable":"no","exploitation":"none","source":"ADP: CISA-ADP","technicalImpact":"total"},"status":"published","title":"Sssd: sssd: idp authentication prefix comparison allows cross-user impersonation","updatedAt":1793689784422}