CVE-2026-6420 | Keylime: keylime: security bypass due to hardcoded tpm quote nonce

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.

Published: 2026-05-06 Last update: 2026-05-07 Assigner: [email protected] Source: [email protected]
NVD Status：Awaiting Analysis，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2026-6420 is rated Low Risk (25.8/100): CVSS Medium severity, with low exploitation likelihood (EPSS 0.01%). Monitor for updates and reassess as exploit intelligence or EPSS changes.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2026-6420

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-05-06 — 0.01% —

Full EPSS history (1 record total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-6420

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
6.3 3.1 MEDIUM
CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:L Click to expand
Attack vector (AV:L)
They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:H)
They need powerful rights—admin, root, or similar—before this pays off.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:L)
Might cause slowdowns, glitches, or partial disruption—not a full brick.
 0.8 5.5 [email protected]

Weakness enumeration for CVE-2026-6420

GitHub Security Advisory for CVE-2026-6420

GHSA-q8w6-w55c-ccv5 · Severity: medium · Ecosystem: pip — Keylime has a hardcoded attestation challenge nonce that allows replay attacks

OS Trackers for CVE-2026-6420

vendor priority summary link
redhat medium — https://access.redhat.com/security/cve/CVE-2026-6420
suse medium — https://www.suse.com/security/cve/CVE-2026-6420/
ubuntu medium CVE-2026-6420 medium priority: Ubuntu has no source package entries, 0 status rows across 0 suites (none): no status rows. https://ubuntu.com/security/CVE-2026-6420

Affected software / configurations for CVE-2026-6420

Vendor Product Version Raw CPE
No affected products in dataset.

References for CVE-2026-6420

cvelogic Threat Intelligence