CVE-2026-34090

Description

Exposure of Sensitive Information to an Unauthorized Actor vulnerability in Wikimedia Foundation CheckUser. This issue affects CheckUser: from 1.45.0 before 1.45.2.

CVSS Details

CVSS Score

7.5

Severity

HIGH

CVSS Vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Configurations (Affected Products)

cpe:2.3:a:mediawiki:checkuser:*:*:*:*:*:mediawiki:*:* - VULNERABLE

Wikimedia Foundation CheckUser >= 1.45.0, < 1.45.2

PoC / Exploit Code

⚠ For Security Research Only

The following code is for security research and authorized testing only.

python

import requests

# Target URL (Example, replace with actual vulnerable endpoint)
target_url = "http://target-wiki-domain/checkuser/sensitive-endpoint"

try:
    # Send a GET request without authentication headers
    response = requests.get(target_url, timeout=10)

    # Check if the request was successful and contains sensitive data
    if response.status_code == 200:
        print("[+] Vulnerability Confirmed!")
        print("[+] Sensitive Data Leaked:")
        print(response.text[:500]) # Print first 500 chars
    else:
        print(f"[-] Request failed with status code: {response.status_code}")
except Exception as e:
    print(f"[-] Error occurred: {e}")

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-34090
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-34090
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-34090/
[4] VulDB https://vuldb.com/cve/CVE-2026-34090
[5] https://phabricator.wikimedia.org/T411366

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-34090", "sourceIdentifier": "c4f26cc8-17ff-4c99-b5e2-38fc1793eacc", "published": "2026-05-11T16:17:30.407", "lastModified": "2026-05-14T16:42:57.203", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "Exposure of Sensitive Information to an Unauthorized Actor vulnerability in Wikimedia Foundation CheckUser.\n\nThis issue affects CheckUser: from 1.45.0 before 1.45.2."}], "metrics": {"cvssMetricV40": [{"source": "c4f26cc8-17ff-4c99-b5e2-38fc1793eacc", "type": "Secondary", "cvssData": {"version": "4.0", "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:P/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:U/V:X/RE:X/U:X", "baseScore": 4.8, "baseSeverity": "MEDIUM", "attackVector": "NETWORK", "attackComplexity": "LOW", "attackRequirements": "NONE", "privilegesRequired": "HIGH", "userInteraction": "PASSIVE", "vulnConfidentialityImpact": "LOW", "vulnIntegrityImpact": "NONE", "vulnAvailabilityImpact": "NONE", "subConfidentialityImpact": "NONE", "subIntegrityImpact": "NONE", "subAvailabilityImpact": "NONE", "exploitMaturity": "NOT_DEFINED", "confidentialityRequirement": "NOT_DEFINED", "integrityRequirement": "NOT_DEFINED", "availabilityRequirement": "NOT_DEFINED", "modifiedAttackVector": "NOT_DEFINED", "modifiedAttackComplexity": "NOT_DEFINED", "modifiedAttackRequirements": "NOT_DEFINED", "modifiedPrivilegesRequired": "NOT_DEFINED", "modifiedUserInteraction": "NOT_DEFINED", "modifiedVulnConfidentialityImpact": "NOT_DEFINED", "modifiedVulnIntegrityImpact": "NOT_DEFINED", "modifiedVulnAvailabilityImpact": "NOT_DEFINED", "modifiedSubConfidentialityImpact": "NOT_DEFINED", "modifiedSubIntegrityImpact": "NOT_DEFINED", "modifiedSubAvailabilityImpact": "NOT_DEFINED", "Safety": "NOT_DEFINED", "Automatable": "NOT_DEFINED", "Recovery": "USER", "valueDensity": "NOT_DEFINED", "vulnerabilityResponseEffort": "NOT_DEFINED", "providerUrgency": "NOT_DEFINED"}}], "cvssMetricV31": [{"source": "[email protected]", "type": "Primary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N", "baseScore": 7.5, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "NONE", "availabilityImpact": "NONE"}, "exploitabilityScore": 3.9, "impactScore": 3.6}]}, "weaknesses": [{"source": "c4f26cc8-17ff-4c99-b5e2-38fc1793eacc", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-200"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:mediawiki:checkuser:*:*:*:*:*:mediawiki:*:*", "versionStartIncluding": "1.45.0", "versionEndExcluding": "1.45.2", "matchCriteriaId": "9BDA6223-EB51-44B8-B817-D6AE2383BA23"}]}]}], "references": [{"url": "https://phabricator.wikimedia.org/T411366", "source": "c4f26cc8-17ff-4c99-b5e2-38fc1793eacc", "tags": ["Issue Tracking", "Patch"]}]}}