---
id: CVE-2026-61500
title: Rejetto HFS < 3.2.1 Session Forgery via Predictable Signing Key
summary: >-
  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 …
severity: critical
cvss: 9.8
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H'
cvssSource: cna
cwe:
  - CWE-338
vendor: rejetto
product: hfs
affected:
  - hfs >= 3.0.0 < 3.2.1
ssvc:
  exploitation: none
  automatable: 'yes'
  technicalImpact: total
  timestamp: '2026-07-15T14:14:22.207797Z'
exploitAvailable: true
published: '2026-07-13'
updated: '2026-10-01'
sourceUpdated: '2026-10-01T15:20:09.180Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-61500'
references:
  - url: 'https://github.com/rejetto/hfs/releases/tag/v3.2.1'
    label: hfs v3.2.1 Release Notes
  - url: >-
      https://www.vulncheck.com/advisories/rejetto-hfs-session-forgery-via-predictable-signing-key
tags:
  - cve.org
  - exploit-available
epss: 0.00857
epssPercentile: 0.56891
exploits:
  github: 1
  githubRepos:
    - 'https://github.com/aramosf/CVE-2026-61500'
  checkedAt: '2026-10-01T15:48:52.501Z'
ingestedAt: '2026-10-01T15:48:17.860Z'
---

## Overview

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

- `hfs >= 3.0.0 < 3.2.1`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.