How severe is CVE-2026-34090?

CVE-2026-34090 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability none.

Is CVE-2026-34090 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (20th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-34090?

CVE-2026-34090 affects Mediawiki Checkuser. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-34090?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

Does CVE-2026-34090 have an EU (EUVD) identifier?

Yes. CVE-2026-34090 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-29062.

When was CVE-2026-34090 published?

CVE-2026-34090 was published on 2026-05-11 and last updated on 2026-06-17.

CVE-2026-34090

CVE-2026-34090 is a high-severity vulnerability in Mediawiki Checkuser with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-200.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v4: 4.8
EPSS exploit prediction: 0% (20th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-29062
Weakness: CWE-200
Affected product: Mediawiki Checkuser
Published: 2026-05-11
Last modified: 2026-06-17

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.

Frequently asked questions

What is CVE-2026-34090?: 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.
How severe is CVE-2026-34090?: CVE-2026-34090 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability none.
Is CVE-2026-34090 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (20th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-34090?: CVE-2026-34090 affects Mediawiki Checkuser. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-34090?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2026-34090 have an EU (EUVD) identifier?: Yes. CVE-2026-34090 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-29062.
When was CVE-2026-34090 published?: CVE-2026-34090 was published on 2026-05-11 and last updated on 2026-06-17.

References

https://phabricator.wikimedia.org/T411366

Affected products (1)

cpe:2.3:a:mediawiki:checkuser:*:*:*:*:*:mediawiki:*:*

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