CVE-2026-61500

CRITICAL 9.8

Rejetto HFS < 3.2.1 Session Forgery via Predictable Signing Key

CVSS Score

9.8

EPSS Score

0.0%

EPSS Percentile

0th

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.

CWE	CWE-338
Vendor	rejetto
Product	hfs
Published	Jul 13, 2026
Last Updated	Jul 15, 2026

Stay Ahead of the Next One

Get instant alerts for rejetto hfs

Be the first to know when new critical vulnerabilities affecting rejetto hfs are published — delivered to Slack, Telegram or Discord.

Get Free Alerts → Free · No credit card · 60 sec setup

CVSS v3 Breakdown

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

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Affected Versions

rejetto / hfs

3.0.0 < 3.2.1

References

NVD ↗ CVE.org ↗ EPSS Data ↗

github.com: https://github.com/rejetto/hfs/releases/tag/v3.2.1 vulncheck.com: https://www.vulncheck.com/advisories/rejetto-hfs-session-forgery-via-predictable-signing-key

Credits

Zach Hanley (@hacks_zach) of Horizon3.ai, in collaboration with Claude and Anthropic Research