CVE-2025-64528: Users are able to find users by name even when `enable_names` is off

Severity: medium (CVSS 5.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-12-30 · updated 2026-06-17
Weakness: CWE-202

Description

Discourse is an open source discussion platform. Prior to versions 3.5.3, 2025.11.1, and 2025.12.0, an attacker who knows part of a username can find the user and their full name via UI or API, even when `enable_names` is disabled. Versions 3.5.3, 2025.11.1, and 2025.12.0 contain a fix.

Affected products

discourse: before 3.5.3; 2025.11.0, 2025.12.0 — fixed in 3.5.3

How to fix

Upgrade to a fixed version: discourse 3.5.3. Check the vendor advisory for mitigations.

References

https://github.com/discourse/discourse/commit/1cb45b8b287597085e3514596ffb1d9b41938f81
https://github.com/discourse/discourse/commit/6192f55629624925595dae14364fd86cac0f09df
https://github.com/discourse/discourse/commit/e936a523b5900a9d866d23ea3da904ba12bb0fb2
https://github.com/discourse/discourse/security/advisories/GHSA-c59w-jwx7-34v4

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