CVE-2021-31552Network attack vector

Account-block bypass and IP disclosure via mistargeted blocks

Published Apr 22, 2021 · Updated Aug 3, 2024

Incorrect authorization in MediaWiki AbuseFilter 1.35.2 and earlier allows remote authenticated users to bypass account blocking. For createaccount matches, the block action targets the account creator's IP instead of the newly created username and exposes that address through block records. A site must enable AbuseFilter and configure a matching account-creation block rule; the resulting account remains usable and creators' IP addresses can be enumerated.

CVSS severity5.4
Medium
EPSS probability0.58%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Incorrect authorization in MediaWiki AbuseFilter 1.35.2 and earlier allows remote authenticated users to bypass account blocking. For createaccount matches, the block action targets the account creator's IP instead of the newly created username and exposes that address through block records. A site must enable AbuseFilter and configure a matching account-creation block rule; the resulting account remains usable and creators' IP addresses can be enumerated.

The record

CVE
CVE-2021-31552
Published
Apr 22, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-863, T1190
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 22, 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?

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

5.5NIST NVDAV:N/AC:L/Au:S/C:P/I:P/A:N
5.4NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N

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 exploitUnconfirmed

Weakness, pattern, technique

CWE-863Incorrect Authorization
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

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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