CVE-2021-32763Public exploitNetwork attack vector

Service interruption via forum quote regex backtracking

Published Jul 20, 2021 · Updated Aug 3, 2024

Regular expression denial of service in OpenProject before 11.3.3 allows remote authenticated users to hang forum quote requests. MessagesController#quote applies a regex whose overlapping dot-or-whitespace alternatives trigger exponential backtracking on an unterminated pre tag filled with spaces. The attacker needs permission to post and quote a forum message; crafted content ties up Ruby processing and interrupts service availability.

CVSS severity4.3
Medium
EPSS probability0.92%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Regular expression denial of service in OpenProject before 11.3.3 allows remote authenticated users to hang forum quote requests. MessagesController#quote applies a regex whose overlapping dot-or-whitespace alternatives trigger exponential backtracking on an unterminated pre tag filled with spaces. The attacker needs permission to post and quote a forum message; crafted content ties up Ruby processing and interrupts service availability.

The record

CVE
CVE-2021-32763
Published
Jul 20, 2021
Updated
Aug 3, 2024
Vendor
OpenProject GmbH
Product
OpenProject
Classifications
CWE-400, T1499.004
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jul 20, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 11.3.3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

OpenProject GmbH · OpenProjectversion=< 11.3.3

Published CVSS scores

4.0NIST NVDAV:N/AC:L/Au:S/C:N/I:N/A:P
4.3GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
6.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-400Uncontrolled Resource Consumption
T1499.004Endpoint Denial of Service: Application or System Exploitation

Public exploit references

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Technologies

Your stack

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Your stack

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