CVE-2023-37303Public exploitNetwork attack vector

Blocking denial of service via unindexed autoblock query

Published Jun 30, 2023 · Updated Nov 27, 2024

Denial of service in the CheckUser extension for MediaWiki 1.39.3 and earlier allows remote authenticated users to make blocking fail. The onPerformRetroactiveAutoblock hook orders a cu_changes lookup by cuc_timestamp without forcing the cuc_actor_ip_time index, causing MariaDB to scan the table until the connection times out. Exploitation requires an account with an unusually large edit history and an administrator to block it with autoblock enabled; the block request hangs and then fails.

CVSS severity9.8
Critical
EPSS probability0.95%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Denial of service in the CheckUser extension for MediaWiki 1.39.3 and earlier allows remote authenticated users to make blocking fail. The onPerformRetroactiveAutoblock hook orders a cu_changes lookup by cuc_timestamp without forcing the cuc_actor_ip_time index, causing MariaDB to scan the table until the connection times out. Exploitation requires an account with an unusually large edit history and an administrator to block it with autoblock enabled; the block request hangs and then fails.

The record

CVE
CVE-2023-37303
Published
Jun 30, 2023
Updated
Nov 27, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-754, T1499.004
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jun 30, 2023CVE publishedPublication date reported by the CVE source.
  2. Nov 27, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

9.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-754Improper Check for Unusual or Exceptional Conditions
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

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo