CVE-2026-34090Network attack vector

Protected-case disclosure via crafted investigation filter

Published May 11, 2026 · Updated May 11, 2026

Information disclosure in Wikimedia Foundation CheckUser 1.45.0 through 1.45.1 allows remote authenticated users to view protected cases. SuggestedInvestigations accepts a crafted username[] URL parameter and returns every case associated with a suppressed username even though the filter form omits that name. Access requires the page permission and prior knowledge of the exact suppressed username; the consequence is limited to disclosure of matching investigation cases.

CVSS severity4.8
Medium
EPSS probability0.28%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Information disclosure in Wikimedia Foundation CheckUser 1.45.0 through 1.45.1 allows remote authenticated users to view protected cases. SuggestedInvestigations accepts a crafted username[] URL parameter and returns every case associated with a suppressed username even though the filter form omits that name. Access requires the page permission and prior knowledge of the exact suppressed username; the consequence is limited to disclosure of matching investigation cases.

The record

CVE
CVE-2026-34090
Published
May 11, 2026
Updated
May 11, 2026
Vendor
Wikimedia Foundation
Product
CheckUser
Classifications
CWE-200, T1213
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. May 11, 2026CVE publishedPublication date reported by the CVE source.
  2. May 11, 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=1.45.0 <1.45.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Wikimedia Foundation · CheckUserversion=1.45.0 <1.45.2

Published CVSS scores

4.8Wikimedia FoundationCVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:P/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N
7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/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.

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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-200Exposure of Sensitive Information to an Unauthorized Actor
T1213Data from Information Repositories

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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