Keylime: keylime: security bypass due to hardcoded tpm quote nonce

{
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "cveMetadata": {
    "cveId": "CVE-2026-6420",
    "assignerOrgId": "53f830b8-0a3f-465b-8143-3b8a9948e749",
    "assignerShortName": "redhat",
    "dateUpdated": "2026-05-06T10:19:39.121Z",
    "dateReserved": "2026-04-16T06:03:46.656Z",
    "datePublished": "2026-05-06T10:19:39.121Z",
    "state": "PUBLISHED"
  },
  "containers": {
    "cna": {
      "providerMetadata": {
        "orgId": "53f830b8-0a3f-465b-8143-3b8a9948e749",
        "shortName": "redhat",
        "dateUpdated": "2026-05-06T10:19:39.121Z"
      },
      "datePublic": "2026-05-06T10:00:00.000Z",
      "title": "Keylime: keylime: security bypass due to hardcoded tpm quote nonce",
      "descriptions": [
        {
          "lang": "en",
          "value": "A flaw was found in Keylime. An attacker with root access on an enrolled monitored machine, where the Keylime agent runs, can exploit a vulnerability in the Keylime verifier. The verifier uses a hardcoded challenge nonce for Trusted Platform Module (TPM) quote attestation instead of a cryptographically random value. This allows the attacker to stockpile valid TPM quotes and replay them to evade detection after compromising the system. This issue affects only the push model deployment."
        }
      ],
      "affected": [
        {
          "vendor": "Red Hat",
          "product": "Red Hat Enterprise Linux 10",
          "collectionURL": "https://access.redhat.com/downloads/content/package-browser/",
          "packageName": "keylime",
          "cpes": [
            "cpe:/o:redhat:enterprise_linux:10"
          ],
          "defaultStatus": "affected"
        },
        {
          "vendor": "Red Hat",
          "product": "Red Hat Enterprise Linux 9",
          "collectionURL": "https://access.redhat.com/downloads/content/package-browser/",
          "packageName": "keylime",
          "cpes": [
            "cpe:/o:redhat:enterprise_linux:9"
          ],
          "defaultStatus": "affected"
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "lang": "en",
              "description": "Use of Predictable Algorithm in Random Number Generator",
              "cweId": "CWE-1241",
              "type": "CWE"
            }
          ]
        }
      ],
      "references": [
        {
          "url": "https://access.redhat.com/security/cve/CVE-2026-6420",
          "tags": [
            "vdb-entry",
            "x_refsource_REDHAT"
          ]
        },
        {
          "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2458889",
          "name": "RHBZ#2458889",
          "tags": [
            "issue-tracking",
            "x_refsource_REDHAT"
          ]
        }
      ],
      "metrics": [
        {},
        {
          "format": "CVSS",
          "cvssV3_1": {
            "version": "3.1",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:L",
            "attackVector": "LOCAL",
            "attackComplexity": "LOW",
            "privilegesRequired": "HIGH",
            "userInteraction": "NONE",
            "scope": "UNCHANGED",
            "confidentialityImpact": "HIGH",
            "integrityImpact": "HIGH",
            "availabilityImpact": "LOW",
            "baseScore": 6.3,
            "baseSeverity": "MEDIUM"
          }
        }
      ],
      "workarounds": [
        {
          "lang": "en",
          "value": "Primary fix (one-line change in keylime/models/verifier/evidence.py):\nBefore (vulnerable):\ndef generate_challenge(self, bit_length):\n\nself.challenge = Nonce.generate(bit_length)\n self.challenge = bytes.fromhex(\"49beed365aac777dae23564f5ad0ec\")\n\nAfter (fixed):\ndef generate_challenge(self, bit_length):\nself.challenge = Nonce.generate(bit_length)\n\nExisting partial mitigations (already active):\n\n1. TPM clock monotonicity check: limits each quote to one replay.\n2. Push attestation timeout (default 10s): constrains the quote generation window, but TPM throughput allows 50-200 quotes to be stockpiled in that time."
        }
      ],
      "timeline": [
        {
          "time": "2026-04-16T06:01:38.993Z",
          "lang": "en",
          "value": "Reported to Red Hat."
        },
        {
          "time": "2026-05-06T10:00:00.000Z",
          "lang": "en",
          "value": "Made public."
        }
      ],
      "credits": [
        {
          "lang": "en",
          "value": "Red Hat would like to thank Keylime developers for reporting this issue."
        }
      ]
    }
  }
}