CVE-2026-6420

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.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

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.