# CVE-2025-40925: Starch versions 0.14 and earlier generate session ids insecurely

> Insecure session ID generation in Starch allows attackers to predict IDs and potentially take over user accounts.

- **Severity:** Critical 9.1 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 20 Sep 2025
- **Updated:** 22 Sep 2025
- **Also known as:** GHSA-q46q-p96m-rvh8

## What is CVE-2025-40925?

CVE-2025-40925 is a critical vulnerability in BLUEFEET Starch, published on 20 Sep 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Starch versions 0.14 and earlier generate session ids insecurely.

The default session id generator returns a SHA-1 hash seeded with a counter, the epoch time, the built-in rand function, the PID, and internal Perl reference addresses. The PID will come from a small set of numbers, and the epoch time may be guessed, if it is not leaked from the HTTP Date header. The built-in rand function is unsuitable for cryptographic usage.

Predicable session ids could allow an attacker to gain access to systems.

Weakness: CWE-340 (Generation of Predictable Numbers or Identifiers), CWE-338 (Use of Cryptographically Weak Pseudo-Random Number Generator (PRNG))

## Which versions are affected by CVE-2025-40925?


## How do I fix CVE-2025-40925?

No fix has been published for CVE-2025-40925 yet. Limit exposure of the affected software until one is available.

## Is CVE-2025-40925 being exploited?

There is no known exploitation of CVE-2025-40925 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-40925 and fix it if it is affected.

What it is: CVE-2025-40925 is a critical vulnerability in BLUEFEET Starch, published on 20 Sep 2025. 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-2025-40925 in the wild and no public exploit code.

Affected product: BLUEFEET Starch. 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-2025-40925/ (Markdown: https://insights.sbomify.com/CVE-2025-40925/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-40925
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-40925
- OSV: https://osv.dev/vulnerability/CVE-2025-40925

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-40925/
Summaries are generated and may contain mistakes; the official description above is the record.