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.
Metrics
Affected Vendors & Products
References
| Link | Providers |
|---|---|
| https://sirius.computer/security-disclosure-policy/ |
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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 |
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| Vendors & Products |
Sirius Computer
Sirius Computer crux Agent |
Fri, 09 Oct 2026 17:30:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Metrics |
ssvc
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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 |
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| References |
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| Metrics |
cvssV4_0
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Status: PUBLISHED
Assigner: sirius
Published: 2026-10-09T13:15:57.779Z
Updated: 2026-10-09T16:46:40.880Z
Reserved: 2026-10-08T20:13:33.223Z
Link: CVE-2026-107785
Updated: 2026-10-09T16:15:28.708Z
Status : Deferred
Published: 2026-10-09T14:17:19.227
Modified: 2026-10-09T17:16:45.597
Link: CVE-2026-107785
No data.