CVE-2026-87853

Full vulnerability record from the local CVENow database.

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.

Severity

HIGH

CVSS score

7.5 (v3.1)

Vulnerability status

Awaiting Analysis

Source identifier

[email protected]

Published

2026-09-09 17:17:52.827000

Last modified

2026-10-29 06:17:24.470000

View original CVE JSON

{
  "id": "CVE-2026-87853",
  "sourceIdentifier": "[email protected]",
  "published": "2026-09-09T17:17:52.827",
  "lastModified": "2026-10-29T06:17:24.470",
  "vulnStatus": "Awaiting Analysis",
  "cveTags": [],
  "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": [
    {
      "source": "[email protected]",
      "affectedData": [
        {
          "vendor": "Red Hat",
          "product": "Red Hat Enterprise Linux 10",
          "defaultStatus": "affected",
          "collectionURL": "https://access.redhat.com/downloads/content/package-browser/",
          "packageName": "sssd",
          "cpes": [
            "cpe:/o:redhat:enterprise_linux:10.2"
          ],
          "versions": [
            {
              "version": "0:2.12.0-3.el10_2.2",
              "lessThan": "*",
              "versionType": "rpm",
              "status": "unaffected"
            }
          ]
        },
        {
          "vendor": "Red Hat",
          "product": "Red Hat Enterprise Linux 6",
          "defaultStatus": "unknown",
          "collectionURL": "https://access.redhat.com/downloads/content/package-browser/",
          "packageName": "sssd",
          "cpes": [
            "cpe:/o:redhat:enterprise_linux:6"
          ]
        },
        {
          "vendor": "Red Hat",
          "product": "Red Hat Enterprise Linux 7",
          "defaultStatus": "unaffected",
          "collectionURL": "https://access.redhat.com/downloads/content/package-browser/",
          "packageName": "sssd",
          "cpes": [
            "cpe:/o:redhat:enterprise_linux:7"
          ]
        },
        {
          "vendor": "Red Hat",
          "product": "Red Hat Enterprise Linux 8",
          "defaultStatus": "unaffected",
          "collectionURL": "https://access.redhat.com/downloads/content/package-browser/",
          "packageName": "sssd",
          "cpes": [
            "cpe:/o:redhat:enterprise_linux:8"
          ]
        },
        {
          "vendor": "Red Hat",
          "product": "Red Hat Enterprise Linux 9",
          "defaultStatus": "unaffected",
          "collectionURL": "https://access.redhat.com/downloads/content/package-browser/",
          "packageName": "sssd",
          "cpes": [
            "cpe:/o:redhat:enterprise_linux:9"
          ]
        },
        {
          "vendor": "Red Hat",
          "product": "Red Hat OpenShift Container Platform 4",
          "defaultStatus": "unaffected",
          "collectionURL": "https://access.redhat.com/downloads/content/package-browser/",
          "packageName": "openshift/ose-rhel-coreos-8",
          "cpes": [
            "cpe:/a:redhat:openshift:4"
          ]
        },
        {
          "vendor": "Red Hat",
          "product": "Red Hat OpenShift Container Platform 4",
          "defaultStatus": "unaffected",
          "collectionURL": "https://access.redhat.com/downloads/content/package-browser/",
          "packageName": "openshift/ose-rhel-coreos-9",
          "cpes": [
            "cpe:/a:redhat:openshift:4"
          ]
        }
      ]
    }
  ],
  "metrics": {
    "cvssMetricV31": [
      {
        "source": "[email protected]",
        "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"
        }
      }
    ]
  },
  "weaknesses": [
    {
      "source": "[email protected]",
      "type": "Secondary",
      "description": [
        {
          "lang": "en",
          "value": "CWE-187"
        }
      ]
    }
  ],
  "references": [
    {
      "url": "https://access.redhat.com/errata/RHSA-2026:77534",
      "source": "[email protected]"
    },
    {
      "url": "https://access.redhat.com/security/cve/CVE-2026-87853",
      "source": "[email protected]"
    },
    {
      "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2530888",
      "source": "[email protected]"
    }
  ]
}