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        "cveId": "CVE-2026-87853",
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        "state": "PUBLISHED",
        "assignerShortName": "redhat",
        "dateReserved": "2026-09-09T13:00:35.698Z",
        "datePublished": "2026-09-09T16:06:25.638Z",
        "dateUpdated": "2026-10-08T23:30:12.939Z"
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    "containers": {
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            "title": "Sssd: sssd: idp authentication prefix comparison allows cross-user impersonation",
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                        "content": {
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                {
                    "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",
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            "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"
                        }
                    ],
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                        "cpe:/o:redhat:enterprise_linux:10.2"
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                },
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                    "vendor": "Red Hat",
                    "product": "Red Hat Enterprise Linux 6",
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                    "packageName": "sssd",
                    "defaultStatus": "unknown",
                    "cpes": [
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                {
                    "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"
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                {
                    "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"
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                {
                    "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"
                    ]
                },
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                    "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"
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                }
            ],
            "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",
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                    ]
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                {
                    "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2530888",
                    "name": "RHBZ#2530888",
                    "tags": [
                        "issue-tracking",
                        "x_refsource_REDHAT"
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                }
            ],
            "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."
                }
            ],
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        "adp": [
            {
                "metrics": [
                    {
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                            "type": "ssvc",
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                                "timestamp": "2026-09-09T18:28:46.606582Z",
                                "id": "CVE-2026-87853",
                                "options": [
                                    {
                                        "Exploitation": "none"
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                                        "Technical Impact": "total"
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                "title": "CISA ADP Vulnrichment",
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