Vulnerability · Published Jul 13, 2026 · Assigned by VulnCheck

CVE-2026-61500Rejetto HFS < 3.2.1 Session Forgery via Predictable Signing Key

Critical 9.8

In plain English

A critical-severity security flaw in hfs from rejetto. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 1.9% (higher than 80% of all known vulnerabilities). Ready-made attack tooling exists: public proof-of-concept code.

Severity (CVSS 3.1)9.8Critical

Exploit odds (30 days)1.9%top 20.1% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack tooling1Public PoC

Official description

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.

Affected products (as reported)

Vendor	Product	Versions
rejetto	hfs	3.0.0 – before 3.2.1

Weakness: CWE-338 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

References

hfs v3.2.1 Release Notes release-notes, patch
https://www.vulncheck.com/advisories/rejetto-hfs-session-forgery-via-predictable-signing-key third-party-advisory