{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-87853","assignerOrgId":"53f830b8-0a3f-465b-8143-3b8a9948e749","state":"PUBLISHED","assignerShortName":"redhat","dateReserved":"2026-09-09T13:00:35.698Z","datePublished":"2026-09-09T16:06:25.638Z","dateUpdated":"2026-10-29T05:30:43.586Z"},"containers":{"cna":{"title":"Sssd: sssd: idp authentication prefix comparison allows cross-user impersonation","metrics":[{"other":{"content":{"value":"Moderate","namespace":"https://access.redhat.com/security/updates/classification/"},"type":"Red Hat severity rating"}},{"cvssV3_1":{"attackComplexity":"HIGH","attackVector":"NETWORK","availabilityImpact":"HIGH","baseScore":7.5,"baseSeverity":"HIGH","confidentialityImpact":"HIGH","integrityImpact":"HIGH","privilegesRequired":"LOW","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H","version":"3.1"},"format":"CVSS"}],"descriptions":[{"lang":"en","value":"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":[{"vendor":"Red Hat","product":"Red Hat Enterprise Linux 10","collectionURL":"https://access.redhat.com/downloads/content/package-browser/","packageName":"sssd","defaultStatus":"affected","versions":[{"version":"0:2.12.0-3.el10_2.2","lessThan":"*","versionType":"rpm","status":"unaffected"}],"cpes":["cpe:/o:redhat:enterprise_linux:10.2"]},{"vendor":"Red Hat","product":"Red Hat Enterprise Linux 6","collectionURL":"https://access.redhat.com/downloads/content/package-browser/","packageName":"sssd","defaultStatus":"unknown","cpes":["cpe:/o:redhat:enterprise_linux:6"]},{"vendor":"Red Hat","product":"Red Hat Enterprise Linux 7","collectionURL":"https://access.redhat.com/downloads/content/package-browser/","packageName":"sssd","defaultStatus":"unaffected","cpes":["cpe:/o:redhat:enterprise_linux:7"]},{"vendor":"Red Hat","product":"Red Hat Enterprise Linux 8","collectionURL":"https://access.redhat.com/downloads/content/package-browser/","packageName":"sssd","defaultStatus":"unaffected","cpes":["cpe:/o:redhat:enterprise_linux:8"]},{"vendor":"Red Hat","product":"Red Hat Enterprise Linux 9","collectionURL":"https://access.redhat.com/downloads/content/package-browser/","packageName":"sssd","defaultStatus":"unaffected","cpes":["cpe:/o:redhat:enterprise_linux:9"]},{"vendor":"Red Hat","product":"Red Hat OpenShift Container Platform 4","collectionURL":"https://access.redhat.com/downloads/content/package-browser/","packageName":"openshift/ose-rhel-coreos-8","defaultStatus":"unaffected","cpes":["cpe:/a:redhat:openshift:4"]},{"vendor":"Red Hat","product":"Red Hat OpenShift Container Platform 4","collectionURL":"https://access.redhat.com/downloads/content/package-browser/","packageName":"openshift/ose-rhel-coreos-9","defaultStatus":"unaffected","cpes":["cpe:/a:redhat:openshift:4"]}],"references":[{"url":"https://access.redhat.com/errata/RHSA-2026:77534","name":"RHSA-2026:77534","tags":["vendor-advisory","x_refsource_REDHAT"]},{"url":"https://access.redhat.com/security/cve/CVE-2026-87853","tags":["vdb-entry","x_refsource_REDHAT"]},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2530888","name":"RHBZ#2530888","tags":["issue-tracking","x_refsource_REDHAT"]}],"datePublic":"2026-09-09T14:15:45.513Z","problemTypes":[{"descriptions":[{"cweId":"CWE-187","description":"Partial String Comparison","lang":"en","type":"CWE"}]}],"x_redhatCweChain":"CWE-187: Partial String Comparison","workarounds":[{"lang":"en","value":"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."}],"timeline":[{"lang":"en","time":"2026-09-06T00:00:00.000Z","value":"Reported to Red Hat."},{"lang":"en","time":"2026-09-09T14:15:45.513Z","value":"Made public."}],"credits":[{"lang":"en","value":"Red Hat would like to thank Moritz Theile for reporting this issue."}],"providerMetadata":{"orgId":"53f830b8-0a3f-465b-8143-3b8a9948e749","shortName":"redhat","dateUpdated":"2026-10-29T05:30:43.586Z"},"x_generator":{"engine":"cvelib 1.8.0"}},"adp":[{"metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-09-09T18:28:46.606582Z","id":"CVE-2026-87853","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"total"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"title":"CISA ADP Vulnrichment","providerMetadata":{"orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","shortName":"CISA-ADP","dateUpdated":"2026-09-10T14:56:49.929Z"}}]}}