Keylime: keylime: security bypass due to hardcoded tpm quote nonce
Summary
| CVE | CVE-2026-6420 |
|---|---|
| State | PUBLISHED |
| Assigner | redhat |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-05-06 11:16:05 UTC |
| Updated | 2026-05-07 14:56:04 UTC |
| 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. |
Risk And Classification
Primary CVSS: v3.1 6.3 MEDIUM from [email protected]
CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:L
EPSS: 0.000160000 probability, percentile 0.037020000 (date 2026-05-12)
Problem Types: CWE-1241 | CWE-1241 Use of Predictable Algorithm in Random Number Generator
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 3.1 | [email protected] | Primary | 6.3 | MEDIUM | CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:L |
| 3.1 | CNA | CVSS | 6.3 | MEDIUM | CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:L |
CVSS v3.1 Breakdown
CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:L
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Red Hat | Red Hat Enterprise Linux 10 | Not specified | Not specified |
| CNA | Red Hat | Red Hat Enterprise Linux 9 | Not specified | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| access.redhat.com/security/cve/CVE-2026-6420 | [email protected] | access.redhat.com | |
| bugzilla.redhat.com/show_bug.cgi | [email protected] | bugzilla.redhat.com | |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
Vendor Comments And Credit
Discovery Credit
CNA: Red Hat would like to thank Keylime developers for reporting this issue. (en)
Additional Advisory Data
| Source | Time | Event |
|---|---|---|
| CNA | 2026-04-16T06:01:38.993Z | Reported to Red Hat. |
| CNA | 2026-05-06T10:00:00.000Z | Made public. |
Workarounds
CNA: 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.