Description
Crux Agent from 1.9.0 before 2.0.3 uses the full SKA bilocation key as the WireGuard preshared key. When a peering session negotiates use of SHA-512, the key produced is 64 bytes instead of the 32 bytes WireGuard requires. The agent does not validate this size; instead it attempts to use the `wg set` command to update the live tunnel, and write the invalid key to the WireGuard configuration file. The update fails, so the live tunnel keeps using its previous preshared key until the tunnel is shut down. The tunnel will fail to start when restarted.



For a peer which has never successfully negotiated a 32-byte bilocation key in a Crux C2 organization which has the "Enforce SKA Use" setting turned off, no preshared key will be set for the tunnel. Therefore, an attacker who is able to intercept and store the peer's traffic, and has access (or will have access) to a cryptographically relevant quantum computer, will be able to decrypt the tunnel.
Published: 2026-10-09
Score: 6.3 Medium
EPSS: < 1% Very Low
KEV: No
Impact: Potential confidentiality compromise via key truncation and failed key rotation
Action: Immediate Patch
AI Analysis

Impact

The Crux Agent, in versions prior to 2.0.3, incorrectly uses the full 64-byte SKA bilocation key as a WireGuard preshared key when a SHA-512 peering session is negotiated. Because WireGuard requires a 32-byte key, the agent fails to validate the size and attempts to update the tunnel through the wg command. The update fails, leaving the tunnel in use with its previous key; if no key was set yet, the tunnel starts without a preshared key. An attacker who can capture the traffic and who has access to a quantum-capable computer could decrypt the tunnel or cause it to fail on restart, breaking confidentiality and availability.

Affected Systems

Affected products include Sirius Computer, Inc.’s Crux Agent, specifically all releases from 1.9.0 up to, but not including, 2.0.3. Systems running these versions and configured to negotiate SHA-512 peering, either with the 'Enforce SKA Use' setting disabled or not, are at risk.

Risk and Exploitability

The vulnerability has a CVSS score of 6.3, reflecting a moderate impact. Exploit probability data is not available, but the flaw is not listed in CISA’s KEV catalog. The primary attack vector appears to be passive interception of traffic coupled with quantum computational capabilities, so widespread exploitation is unlikely without the attacker’s specialized equipment and the system’s configuration permitting SHA-512 peering.

Generated by OpenCVE AI on October 9, 2026 at 14:52 UTC.

Remediation

Vendor Solution

Upgrade to Crux Agent 2.0.3 or later, which truncates the SKA key to the 32 bytes WireGuard requires. As a workaround, remove any custom settings for "Hash Function" in the agent's configuration (so as to use the default SHA-256 hash function).

OpenCVE Recommended Actions

  • Upgrade to Crux Agent 2.0.3 or later, which truncates the SKA key to the required 32 bytes.
  • As a temporary workaround, remove any custom "Hash Function" configuration so that the agent uses the default SHA-256 hash function.
  • Ensure that the system’s peering configuration does not mandate SHA-512 and that the 'Enforce SKA Use' policy is only enabled when necessary.

Generated by OpenCVE AI on October 9, 2026 at 14:52 UTC.

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History

Sun, 11 Oct 2026 12:45:00 +0000

Type Values Removed Values Added
First Time appeared Sirius Computer
Sirius Computer crux Agent
Vendors & Products Sirius Computer
Sirius Computer crux Agent

Fri, 09 Oct 2026 17:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

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

Fri, 09 Oct 2026 13:30:00 +0000

Type Values Removed Values Added
Description Crux Agent from 1.9.0 before 2.0.3 uses the full SKA bilocation key as the WireGuard preshared key. When a peering session negotiates use of SHA-512, the key produced is 64 bytes instead of the 32 bytes WireGuard requires. The agent does not validate this size; instead it attempts to use the `wg set` command to update the live tunnel, and write the invalid key to the WireGuard configuration file. The update fails, so the live tunnel keeps using its previous preshared key until the tunnel is shut down. The tunnel will fail to start when restarted. For a peer which has never successfully negotiated a 32-byte bilocation key in a Crux C2 organization which has the "Enforce SKA Use" setting turned off, no preshared key will be set for the tunnel. Therefore, an attacker who is able to intercept and store the peer's traffic, and has access (or will have access) to a cryptographically relevant quantum computer, will be able to decrypt the tunnel.
Title Crux Agent silently fails SKA preshared key rotation when SHA-512 peering is negotiated
Weaknesses CWE-252
CWE-325
CWE-394
References
Metrics cvssV4_0

{'score': 6.3, 'vector': 'CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:H/SI:N/SA:N/E:U/S:N/AU:Y/R:A/V:C/RE:L/U:Amber'}

Subscriptions

Sirius Computer Crux Agent
cve-icon MITRE

Status: PUBLISHED

Assigner: sirius

Published:

Updated: 2026-10-09T16:46:40.880Z

Reserved: 2026-10-08T20:13:33.223Z

Link: CVE-2026-107785

cve-icon Vulnrichment

Updated: 2026-10-09T16:15:28.708Z

cve-icon NVD

Status : Deferred

Published: 2026-10-09T14:17:19.227

Modified: 2026-10-09T17:16:45.597

Link: CVE-2026-107785

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-10-11T12:27:21Z

Weaknesses
  • CWE-252

    Unchecked Return Value

  • CWE-325

    Missing Cryptographic Step

  • CWE-394

    Unexpected Status Code or Return Value