Vulnerability · Published May 11, 2026 · Assigned by wikimedia-foundation
CVE-2026-34090Suggested investigations: Handle suppressed usernames
Medium 4.8
In plain English
A medium-severity information exposure in CheckUser from Wikimedia Foundation. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 21% of all known vulnerabilities).
Severity (CVSS 4.0)4.8Medium
Exploit odds (30 days)0.3%top 79.4% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:14 | mediawiki | no fix listed | DEBIAN-CVE-2026-34090 |
| Ubuntu:22.04:LTS | mediawiki | no fix listed | UBUNTU-CVE-2026-34090 |
| Ubuntu:24.04:LTS | mediawiki | no fix listed | UBUNTU-CVE-2026-34090 |
| Ubuntu:25.10 | mediawiki | no fix listed | UBUNTU-CVE-2026-34090 |
| Ubuntu:26.04:LTS | mediawiki | no fix listed | UBUNTU-CVE-2026-34090 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Wikimedia Foundation | CheckUser | 1.45.0 – before 1.45.2 |
Weakness: CWE-200 · Vector: 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/R:U