CVE-2024-21655: Insufficient control of custom field value sizes

Severity: medium (CVSS 4.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.6% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2024-01-12 · updated 2026-06-17
Weakness: CWE-400

Description

Discourse is a platform for community discussion. For fields that are client editable, limits on sizes are not imposed. This allows a malicious actor to cause a Discourse instance to use excessive disk space and also often excessive bandwidth. The issue is patched 3.1.4 and 3.2.0.beta4.

Affected products

discourse: before 3.1.4; 3.2.0-beta1, 3.2.0-beta2, 3.2.0-beta3 — fixed in 3.1.4

How to fix

Upgrade to a fixed version: discourse 3.1.4. Check the vendor advisory for mitigations.

References

https://github.com/discourse/discourse/security/advisories/GHSA-m5fc-94mm-38fx
https://github.com/discourse/discourse/security/advisories/GHSA-m5fc-94mm-38fx

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