Keylime has a hardcoded attestation challenge nonce that allows replay attacks

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

6.3 · CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:L

EPSS

• CVE-2026-6420: 0.12% estimated exploitation activity in the next 30 days; percentile 1.91 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

CVE-2026-6420: Hardcoded attestation challenge nonce allows replay attacks Impact The CertificationParameters.generatechallenge() method in the push attestation protocol uses a hardcoded challenge nonce instead of generating a cryptographically random value. This removes the nonce-based replay protection from TPM quote attestation. An attacker with root access on a monitored agent node can exploit this by stockpiling valid TPM quotes (using tpm2quote with the known nonce) before compromising the system, then replaying them to evade detection by the verifier. The push attestation timeout (~10s) constrains the generation window, but TPM throughput allows stockpiling ~50-200 quotes, enabling approximately 8-33 minutes of undetected compromise with default settings. The attack is limited to a single agent node (AK signature binding prevents cross-agent replay). The pull-mode (legacy) attestation path is not affected. Affected versions: = 7.14.0, <= 7.14.1 CVSS: 6.3 Medium…

Published by the source

11 May 2026, 14:42 UTC

Last modified by the source

13 Jul 2026, 16:43 UTC

Source last checked

26 Oct 2026, 13:41 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-q8w6-w55c-ccv5

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-q8w6-w55c-ccv5

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# Patch Next advisory brief: CVE-2026-6420

Advisory: Keylime has a hardcoded attestation challenge nonce that allows replay attacks
IDs: CVE-2026-6420, GHSA-q8w6-w55c-ccv5
Record: https://patchnext.com/advisories/cve-2026-6420 (revision 2, source checked 26 Oct 2026, 13:41 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: keylime 7.14.2. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI keylime: affected >= 7.14.0, <= 7.14.1; fixed in 7.14.2

## Suggested inspection (read-only)
- `python -m pip show keylime`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on keylime.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-q8w6-w55c-ccv5 (OSV record GHSA-q8w6-w55c-ccv5 lists affected ranges: PyPI keylime >=7.14.0 <7.14.2 (fixed))
- Verified: https://github.com/advisories/GHSA-q8w6-w55c-ccv5 (GitHub-reviewed advisory GHSA-q8w6-w55c-ccv5 lists affected ranges: PyPI keylime >=7.14.0 <=7.14.1)

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