# CVE-2025-40916: Mojolicious::Plugin::CaptchaPNG version 1.05 for Perl uses a weak random number source for generating the captcha text

> Attackers can bypass captcha protections because the plugin uses a weak random number generator for captcha text and noise.

- **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:** 16 Jun 2025
- **Updated:** 16 Jun 2025
- **Also known as:** GHSA-w6w2-2wxg-ggwx

## What is CVE-2025-40916?

CVE-2025-40916 is a critical vulnerability in GRYPHON Mojolicious::Plugin::CaptchaPNG, published on 16 Jun 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Mojolicious::Plugin::CaptchaPNG version 1.05 for Perl uses a weak random number source for generating the captcha.

That version uses the built-in rand() function for generating the captcha text as well as image noise, which is insecure.

Weakness: CWE-804 (Guessable CAPTCHA), CWE-338 (Use of Cryptographically Weak Pseudo-Random Number Generator (PRNG))

## Which versions are affected by CVE-2025-40916?


## How do I fix CVE-2025-40916?

No fix has been published for CVE-2025-40916 yet. Limit exposure of the affected software until one is available.

## Is CVE-2025-40916 being exploited?

There is no known exploitation of CVE-2025-40916 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-40916 and fix it if it is affected.

What it is: CVE-2025-40916 is a critical vulnerability in GRYPHON Mojolicious::Plugin::CaptchaPNG, published on 16 Jun 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-2025-40916 in the wild and no public exploit code.

Affected product: GRYPHON Mojolicious::Plugin::CaptchaPNG. 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-2025-40916/ (Markdown: https://insights.sbomify.com/CVE-2025-40916/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-40916
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-40916
- OSV: https://osv.dev/vulnerability/CVE-2025-40916

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-40916/
Summaries are generated and may contain mistakes; the official description above is the record.