Crux Agent silently fails SKA preshared key rotation when SHA-512 peering is negotiated
Summary
| CVE | CVE-2026-107785 |
|---|---|
| State | PUBLISHED |
| Assigner | sirius |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-10-09 14:17:19 UTC |
| Updated | 2026-10-09 17:16:45 UTC |
| 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. |
Risk And Classification
Primary CVSS: v4.0 6.3 MEDIUM from d0a6edd6-4b7d-45f2-a6f9-9b944f7b6132
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/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:N/AU:Y/R:A/V:C/RE:L/U:Amber
EPSS: 0.001380000 probability, percentile 0.027360000 (date 2026-10-11)
Problem Types: CWE-252 | CWE-325 | CWE-394 | CWE-394 CWE-394: Unexpected Status Code or Return Value | CWE-252 CWE-252: Unchecked Return Value | CWE-325 CWE-325: Missing Cryptographic Step
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 4.0 | d0a6edd6-4b7d-45f2-a6f9-9b944f7b6132 | Secondary | 6.3 | MEDIUM | 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/C... |
| 4.0 | CNA | CVSS | 6.3 | MEDIUM | 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... |
CVSS v4.0 Breakdown
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/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:N/AU:Y/R:A/V:C/RE:L/U:Amber
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Sirius Computer Inc. | Crux Agent | affected 1.9.0 2.0.3 semver | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| sirius.computer/security-disclosure-policy | d0a6edd6-4b7d-45f2-a6f9-9b944f7b6132 | sirius.computer | |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
Additional Advisory Data
Solutions
CNA: 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).