CVE-2026-6420

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

Published May 6, 2026 CVSS 3.1 · 6.3 Medium EPSS < 1% KEV · Not listed
Description
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.

Remediation

Vendor Workaround

Primary fix (one-line change in keylime/models/verifier/evidence.py): Before (vulnerable): def generate_challenge(self, bit_length): self.challenge = Nonce.generate(bit_length) self.challenge = bytes.fromhex("49beed365aac777dae23564f5ad0ec") After (fixed): def generate_challenge(self, bit_length): self.challenge = Nonce.generate(bit_length) Existing partial mitigations (already active): 1. TPM clock monotonicity check: limits each quote to one replay. 2. Push attestation timeout (default 10s): constrains the quote generation window, but TPM throughput allows 50-200 quotes to be stockpiled in that time.

Tracking

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Advisories

Source ID Title
Github GHSA Github GHSA GHSA-q8w6-w55c-ccv5 Keylime has a hardcoded attestation challenge nonce that allows replay attacks
History
Type Values Removed Values Added
CPEs cpe:/o:redhat:enterprise_linux:9 cpe:/a:redhat:enterprise_linux:9
Type Values Removed Values Added
CPEs cpe:/o:redhat:enterprise_linux:10 cpe:/o:redhat:enterprise_linux:10.2
References
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}

Type Values Removed Values Added
Description 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.
Title Keylime: keylime: security bypass due to hardcoded tpm quote nonce
First Time appeared Redhat
Redhat enterprise Linux
Weaknesses CWE-1241
CPEs cpe:/o:redhat:enterprise_linux:10
cpe:/o:redhat:enterprise_linux:9
Vendors & Products Redhat
Redhat enterprise Linux
References
Metrics cvssV3_1

{'score': 6.3, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:L'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
redhat
Published
Updated
Nov 5, 2026, 9:55 PM
Reserved
Apr 16, 2026, 6:03 AM
Status
Awaiting Analysis
Published
May 6, 2026, 11:16 AM
Modified
Nov 5, 2026, 10:18 PM
Severity
Moderate
Public date
May 6, 2026, 10:00 AM