{"api_version":"1","generated_at":"2026-09-11T03:26:17+00:00","cve":"CVE-2026-87853","urls":{"html":"https://cve.report/CVE-2026-87853","api":"https://cve.report/api/cve/CVE-2026-87853.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-87853","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-87853"},"summary":{"title":"Sssd: sssd: idp authentication prefix comparison allows cross-user impersonation","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.","state":"PUBLISHED","assigner":"redhat","published_at":"2026-09-09 17:17:52","updated_at":"2026-09-10 15:17:54"},"problem_types":["CWE-187","CWE-187 Partial String Comparison"],"metrics":[{"version":"3.1","source":"secalert@redhat.com","type":"Secondary","score":"7.5","severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H","data":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7.5,"baseSeverity":"HIGH","attackVector":"NETWORK","attackComplexity":"HIGH","privilegesRequired":"LOW","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH"}},{"version":"3.1","source":"CNA","type":"CVSS","score":"7.5","severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H","data":{"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"}}],"references":[{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2530888","name":"https://bugzilla.redhat.com/show_bug.cgi?id=2530888","refsource":"secalert@redhat.com","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://access.redhat.com/security/cve/CVE-2026-87853","name":"https://access.redhat.com/security/cve/CVE-2026-87853","refsource":"secalert@redhat.com","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-87853","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-87853","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Red Hat","product":"Red Hat Enterprise Linux 10","version":"","platforms":[]},{"source":"CNA","vendor":"Red Hat","product":"Red Hat Enterprise Linux 6","version":"","platforms":[]},{"source":"CNA","vendor":"Red Hat","product":"Red Hat Enterprise Linux 7","version":"","platforms":[]},{"source":"CNA","vendor":"Red Hat","product":"Red Hat Enterprise Linux 8","version":"","platforms":[]},{"source":"CNA","vendor":"Red Hat","product":"Red Hat Enterprise Linux 9","version":"","platforms":[]},{"source":"CNA","vendor":"Red Hat","product":"Red Hat OpenShift Container Platform 4","version":"","platforms":[]},{"source":"CNA","vendor":"Red Hat","product":"Red Hat OpenShift Container Platform 4","version":"","platforms":[]}],"timeline":[{"source":"CNA","time":"2026-09-06T00:00:00.000Z","lang":"en","value":"Reported to Red Hat."},{"source":"CNA","time":"2026-09-09T14:15:45.513Z","lang":"en","value":"Made public."}],"solutions":[],"workarounds":[{"source":"CNA","title":"","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.","time":"","lang":"en"}],"exploits":[],"credits":[{"source":"CNA","value":"Red Hat would like to thank Moritz Theile for reporting this issue.","lang":"en"}],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":{"cve_year":"2026","cve_id":"87853","cve":"CVE-2026-87853","epss":"0.002810000","percentile":"0.203950000","score_date":"2026-09-10","updated_at":"2026-09-11 00:05:16"},"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"adp":[{"metrics":[{"other":{"content":{"id":"CVE-2026-87853","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"total"}],"role":"CISA Coordinator","timestamp":"2026-09-09T18:28:46.606582Z","version":"2.0.3"},"type":"ssvc"}}],"providerMetadata":{"dateUpdated":"2026-09-10T14:56:49.929Z","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","shortName":"CISA-ADP"},"title":"CISA ADP Vulnrichment"}],"cna":{"affected":[{"collectionURL":"https://access.redhat.com/downloads/content/package-browser/","cpes":["cpe:/o:redhat:enterprise_linux:10"],"defaultStatus":"affected","packageName":"sssd","product":"Red Hat Enterprise Linux 10","vendor":"Red Hat"},{"collectionURL":"https://access.redhat.com/downloads/content/package-browser/","cpes":["cpe:/o:redhat:enterprise_linux:6"],"defaultStatus":"unknown","packageName":"sssd","product":"Red Hat Enterprise Linux 6","vendor":"Red Hat"},{"collectionURL":"https://access.redhat.com/downloads/content/package-browser/","cpes":["cpe:/o:redhat:enterprise_linux:7"],"defaultStatus":"unaffected","packageName":"sssd","product":"Red Hat Enterprise Linux 7","vendor":"Red Hat"},{"collectionURL":"https://access.redhat.com/downloads/content/package-browser/","cpes":["cpe:/o:redhat:enterprise_linux:8"],"defaultStatus":"unaffected","packageName":"sssd","product":"Red Hat Enterprise Linux 8","vendor":"Red Hat"},{"collectionURL":"https://access.redhat.com/downloads/content/package-browser/","cpes":["cpe:/o:redhat:enterprise_linux:9"],"defaultStatus":"unaffected","packageName":"sssd","product":"Red Hat Enterprise Linux 9","vendor":"Red Hat"},{"collectionURL":"https://access.redhat.com/downloads/content/package-browser/","cpes":["cpe:/a:redhat:openshift:4"],"defaultStatus":"unaffected","packageName":"openshift/ose-rhel-coreos-8","product":"Red Hat OpenShift Container Platform 4","vendor":"Red Hat"},{"collectionURL":"https://access.redhat.com/downloads/content/package-browser/","cpes":["cpe:/a:redhat:openshift:4"],"defaultStatus":"unaffected","packageName":"openshift/ose-rhel-coreos-9","product":"Red Hat OpenShift Container Platform 4","vendor":"Red Hat"}],"credits":[{"lang":"en","value":"Red Hat would like to thank Moritz Theile for reporting this issue."}],"datePublic":"2026-09-09T14:15:45.513Z","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."}],"metrics":[{"other":{"content":{"namespace":"https://access.redhat.com/security/updates/classification/","value":"Moderate"},"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"}],"problemTypes":[{"descriptions":[{"cweId":"CWE-187","description":"Partial String Comparison","lang":"en","type":"CWE"}]}],"providerMetadata":{"dateUpdated":"2026-09-09T16:06:25.638Z","orgId":"53f830b8-0a3f-465b-8143-3b8a9948e749","shortName":"redhat"},"references":[{"tags":["vdb-entry","x_refsource_REDHAT"],"url":"https://access.redhat.com/security/cve/CVE-2026-87853"},{"name":"RHBZ#2530888","tags":["issue-tracking","x_refsource_REDHAT"],"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2530888"}],"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."}],"title":"Sssd: sssd: idp authentication prefix comparison allows cross-user impersonation","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."}],"x_generator":{"engine":"cvelib 1.8.0"},"x_redhatCweChain":"CWE-187: Partial String Comparison"}},"cveMetadata":{"assignerOrgId":"53f830b8-0a3f-465b-8143-3b8a9948e749","assignerShortName":"redhat","cveId":"CVE-2026-87853","datePublished":"2026-09-09T16:06:25.638Z","dateReserved":"2026-09-09T13:00:35.698Z","dateUpdated":"2026-09-10T14:56:49.929Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-09-09 17:17:52","lastModifiedDate":"2026-09-10 15:17:54","problem_types":["CWE-187","CWE-187 Partial String Comparison"],"metrics":{"cvssMetricV31":[{"source":"secalert@redhat.com","type":"Secondary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7.5,"baseSeverity":"HIGH","attackVector":"NETWORK","attackComplexity":"HIGH","privilegesRequired":"LOW","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH"},"exploitabilityScore":1.6,"impactScore":5.9}],"ssvcV203":[{"source":"134c704f-9b21-4f2e-91b3-4a467353bcc0","ssvcData":{"timestamp":"2026-09-09T18:28:46.606582Z","id":"CVE-2026-87853","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"total"}],"role":"CISA Coordinator","version":"2.0.3"}}]},"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"87853","Ordinal":"1","Title":"Sssd: sssd: idp authentication prefix comparison allows cross-us","CVE":"CVE-2026-87853","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"87853","Ordinal":"1","NoteData":"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.","Type":"Description","Title":"Sssd: sssd: idp authentication prefix comparison allows cross-us"}]}}}