# CVE-2026-61500: Rejetto HFS session cookie signing key forgery in HFS 3.x

Source: https://junglewise.ai/threats/cve-2026-61500-rejetto-hfs-session-cookie-signing-key-forgery-in-hfs-3-x  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-07-13. Updated: 2026-07-13  
License: CC BY 4.0 with a link back

CVE-2026-61500 · Severity: critical · CVSS 9.8 · Published 2026-07-13

Rejetto HFS, a popular file-sharing server, contains a security flaw in how it secures user sessions. An attacker can predict the secret keys used to sign login cookies by observing a few login attempts. This allows an unauthorized person to impersonate an administrator, take full control of the server, and execute malicious code, potentially leading to a complete system takeover and data theft.

Technologies: [Rejetto HFS (HTTP File Server)](https://junglewise.ai/threats/technologies/hfs-http-file-server). Vendors: [Rejetto](https://junglewise.ai/threats/vendors/rejetto).

## Quick answers

**Is CVE-2026-61500 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-61500 being exploited in the wild.

**How severe is CVE-2026-61500?** Critical severity, with a CVSS score of 9.8, published 13 July 2026.

**Which products and versions are affected?** Rejetto HFS (HTTP File Server) 3.0.0 through 3.2.0.

**Is there a fix for CVE-2026-61500?** A patch was published on 2026-07-13: Fixed in version 3.2.1 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-61500 attacked?** It is attacked over the network, in a network appliance.

**Am I affected by CVE-2026-61500?** Check whether you run Rejetto HFS (HTTP File Server) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

Rejetto HFS (versions 3.0.0 to 3.2.0) utilizes the non-cryptographic Math.random() generator to derive its session-cookie signing key. Because the application also discloses outputs from this same generator to unauthenticated clients during the login process, a remote attacker can collect a small number of responses to reconstruct the PRNG state. Once the state is known, the attacker can recover the signing key and forge a valid administrator session cookie. With administrative access, the attacker can leverage the 'server_code' configuration feature to achieve remote code execution (RCE). The vulnerability is addressed in version 3.2.1.

## Affected products

- Rejetto HFS (HTTP File Server) 3.0.0 through 3.2.0

## Timeline

- 2026-07-13: disclosed
- 2026-07-13: patched: Fixed in version 3.2.1
- 2026-07-13: advisory

## References

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

## Related threats

- [Rejetto HFS path traversal in lang parameter](https://junglewise.ai/threats/cve-2026-61505-rejetto-hfs-path-traversal-in-lang-parameter)
- [Rejetto HFS stored XSS in basic web listing via file names](https://junglewise.ai/threats/cve-2026-61504-rejetto-hfs-stored-xss-in-basic-web-listing-via-file-names)