CVE-2021-32763: Regular Expression Denial of Service in OpenProject forum messages

Severity: medium (CVSS 6.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.9% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-07-20 · updated 2026-06-17
Weakness: CWE-400

Description

OpenProject is open-source, web-based project management software. In versions prior to 11.3.3, the `MessagesController` class of OpenProject has a `quote` method that implements the logic behind the Quote button in the discussion forums, and it uses a regex to strip `<pre>` tags from the message being quoted. The `(.|\s)` part can match a space character in two ways, so an unterminated `<pre>` tag containing `n` spaces causes Ruby's regex engine to backtrack to try 2<sup>n</sup> states in the NFA. This will result in a Regular Expression Denial of Service. The issue is fixed in OpenProject 11.3.3. As a workaround, one may install the patch manually.

Affected products

opf openproject: before 11.3.3 — fixed in 11.3.3

How to fix

Upgrade to a fixed version: opf openproject 11.3.3. Check the vendor advisory for mitigations.

References

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