CVE-2023-3994Public exploitNetwork attack vector

Service interruption via ProjectReferenceFilter regex backtracking

Published Aug 2, 2023 · Updated Apr 27, 2026

Regular expression denial of service in affected GitLab CE/EE versions allows remote attackers to interrupt service via Markdown previews. ReferenceFilter#replace_text_when_pattern_matches applies Project.markdown_reference_pattern to attacker-controlled Markdown; a missing terminal > or > causes severe backtracking. Unauthenticated access to a public group's preview endpoint and a session CSRF token are sufficient; sustained requests exhaust worker CPUs until the instance becomes unresponsive.

CVSS severity7.5
High
EPSS probability0.96%
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 affected GitLab CE/EE versions allows remote attackers to interrupt service via Markdown previews. ReferenceFilter#replace_text_when_pattern_matches applies Project.markdown_reference_pattern to attacker-controlled Markdown; a missing terminal > or > causes severe backtracking. Unauthenticated access to a public group's preview endpoint and a session CSRF token are sufficient; sustained requests exhaust worker CPUs until the instance becomes unresponsive.

The record

CVE
CVE-2023-3994
Published
Aug 2, 2023
Updated
Apr 27, 2026
Vendor
GitLab
Product
GitLab
Classifications
CWE-1333, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 2, 2023CVE publishedPublication date reported by the CVE source.
  2. Apr 27, 2026Record 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=16.1 <16.1.3
  2. Affected versionversion=16.2 <16.2.2
  3. Affected versionversion=9.3 <16.0.8

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

GitLab · GitLabversion=16.1 <16.1.3; version=16.2 <16.2.2; version=9.3 <16.0.8

Published CVSS scores

7.5GitLab Inc.CVSS:3.1/AV:N/AC:L/PR:N/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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-1333Inefficient Regular Expression Complexity
T1499.004Application or System Exploitation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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