What is this vulnerability?

Rejetto HFS 3.0.0 through 3.2.0 derives its session-cookie signing key from the non-cryptographic Math.random() generator and discloses outputs of the same generator to unauthenticated clients during login. A remote attacker can collect a small number of login responses, reconstruct the generator's state, recover the signing key, and forge a valid administrator session cookie, leading to full administrative access and remote code execution via the server_code configuration feature.

How it works

This is classified as CWE-338. In plain terms, an attacker could use this flaw in the affected product to gain access, disrupt service, or steal data — the exact impact depends on how it’s deployed in your environment.

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

Mitigations

• Apply the vendor’s security patch or update as soon as it’s available and tested.
• If no patch exists yet, apply the vendor’s temporary workaround.
• Limit network exposure of the affected system until it’s patched.
• Track the vendor advisory — disclosed vulnerabilities can move to active exploitation quickly.

Recommendations

• Confirm whether this vendor’s affected product is used anywhere in your environment.
• Patch internet-facing systems first, then internal ones.
• Prioritise by exposure and exploitability while a fix is scheduled.
• Subscribe to the vendor’s security advisories for earlier warning next time.