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

> Remote attackers can forge admin sessions by predicting weak signing keys, leading to full administrative access and remote code execution.

- **Severity:** Critical 9.3 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 13 Jul 2026
- **Updated:** 1 Oct 2026
- **Also known as:** GHSA-xxrm-3f86-v97j

## What is CVE-2026-61500?

CVE-2026-61500 is a critical vulnerability in rejetto hfs, published on 13 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### 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.

Weakness: CWE-338 (Use of Cryptographically Weak Pseudo-Random Number Generator (PRNG))

## Which versions are affected by CVE-2026-61500?


## How do I fix CVE-2026-61500?

No fix has been published for CVE-2026-61500 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-61500 being exploited?

There is no known exploitation of CVE-2026-61500 in the wild and no public exploit code.

Public exploit code:

- CVE-2026-61500 Rejetto HFS predictable PRNG session forgery to RCE PoC and Docker lab (github_poc): https://github.com/aramosf/CVE-2026-61500

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-61500 and fix it if it is affected.

What it is: CVE-2026-61500 is a critical vulnerability in rejetto hfs, published on 13 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-61500 in the wild and no public exploit code.

Affected product: rejetto hfs. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-61500/ (Markdown: https://insights.sbomify.com/CVE-2026-61500/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-61500
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-61500
- OSV: https://osv.dev/vulnerability/CVE-2026-61500

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-61500/
Summaries are generated and may contain mistakes; the official description above is the record.