CVE-2026-61500

Think of this software's login system like a safe whose combination is generated by a cheap, guessable shuffle instead of a real lock. An attacker who watches a few login attempts can figure out the pattern, 'guess' the admin combination, and walk in with full control — including the ability to run their own commands on your server.

This matters to you if you run Rejetto HFS (HTTP File Server) to share or host files, specifically any version from 3.0.0 through 3.2.0. The flaw requires no valid account and no user interaction — anyone who can reach the server's login page over the network can attempt the attack, so exposure is highest if the HFS admin interface is reachable from the internet.

This is a critical, unauthenticated path to full administrative control and code execution on the server, requiring no special skill beyond collecting a handful of login responses — a low bar for any attacker who finds the server online. There's no confirmed active exploitation or public exploit code yet, but given how trivial the weakness is to exploit once understood and the sustained press attention around it, you should patch now rather than wait for proof of attacks.

Confirm your deployed HFS version; any instance in the 3.0.0–3.2.0 range is vulnerable. Upgrade to 3.2.1 or later, which replaces the Math.random()-based signing key derivation with a cryptographically secure generator and stops leaking generator state to unauthenticated clients. There is no documented breaking-change concern for this upgrade. If immediate patching isn't possible, take the admin interface off any public-facing network, restrict access via firewall/VPN to trusted IPs, and disable the server_code feature if enabled, since it's the RCE vector once a session is forged. After upgrading, restart the service to rotate the signing key and invalidate existing sessions. There is no CISA KEV listing or due date for this CVE at this time. Monitor web/access logs for repeated login attempts followed by admin-level actions, unexpected changes to server_code or configuration, and any outbound connections initiated from the HFS host, as indicators of compromise given the sustained press interest tied to actor ShinyHunters.

CVSS 9.8 (Critical), AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H — network-exploitable, no privileges or user interaction required, full compromise of confidentiality, integrity and availability. Weakness is CWE-338 (Use of Cryptographically Weak PRNG): the session-cookie signing key is derived from Math.random(), and its outputs are disclosed to unauthenticated clients during login, enabling state reconstruction and session/cookie forgery leading to admin takeover and RCE via server_code. Not listed in CISA KEV; no public exploit code found. EPSS predicts low near-term exploitation likelihood with a flat trend, but this should not be read as safe given the low attack complexity and critical impact. Exploit maturity is currently theoretical/PoC-level per available findings, though sustained press coverage referencing actor ShinyHunters suggests active interest in the vulnerability class.