CVE-2021-30156

An issue was discovered in MediaWiki before 1.31.12 and 1.32.x through 1.35.x before 1.35.2....

4.3 MediumFix available

An issue was discovered in MediaWiki before 1.31.12 and 1.32.x through 1.35.x before 1.35.2. Special:Contributions can leak that a "hidden" user exists.

Attack profile

How easy it is to exploit

Attack vector: Network
Complexity: Low
Privileges needed: Low
User interaction: None

What an attacker can affect

Confidentiality: None
Integrity: Low
Availability: None

Exploit likelihood

1.14%Up 0.7 points since Apr 14, 2021

What each source reports

NVD Score used 4.3

An issue was discovered in MediaWiki before 1.31.12 and 1.32.x through 1.35.x before 1.35.2. Special:Contributions can leak that a "hidden" user exists.

Record: CVE-2021-30156
CVSS 3.1: 4.3 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N
CVSS 2.0: 4.0 MediumAV:N/AC:L/Au:S/C:N/I:P/A:N
Weakness: CWE-200
Updated: 2026-11-02

CVE List No score

An issue was discovered in MediaWiki before 1.31.12 and 1.32.x through 1.35.x before 1.35.2. Special:Contributions can leak that a "hidden" user exists.

Record: CVE-2021-30156
Updated: 2026-11-02

EUVDEUVD-2021-17092 No score

An issue was discovered in MediaWiki before 1.31.12 and 1.32.x through 1.35.x before 1.35.2. Special:Contributions can leak that a "hidden" user exists.

Record: EUVD-2021-17092
Updated: 2026-11-03

GitHub AdvisoriesGHSA-4w3g-mpj2-j247 4.3

An issue was discovered in MediaWiki before 1.31.12 and 1.32.x through 1.35.x before 1.35.2....

An issue was discovered in MediaWiki before 1.31.12 and 1.32.x through 1.35.x before 1.35.2. Special:Contributions can leak that a "hidden" user exists.

Record: GHSA-4w3g-mpj2-j247
CVSS 3.1: 4.3 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N
Weakness: CWE-732
Updated: 2026-11-02

OSV 4.3

An issue was discovered in MediaWiki before 1.31.12 and 1.32.x through 1.35.x before 1.35.2. Special:Contributions can leak that a "hidden" user exists.

Record: CVE-2021-30156
CVSS 3.1: 4.3 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N
Updated: 2026-11-02

OSVUBUNTU-CVE-2021-30156 4.3

An issue was discovered in MediaWiki before 1.31.12 and 1.32.x through 1.35.x before 1.35.2. Special:Contributions can leak that a "hidden" user exists.

Record: UBUNTU-CVE-2021-30156
CVSS 3.1: 4.3 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N
Updated: 2026-11-02

OSVBIT-mediawiki-2021-30156 No score

An issue was discovered in MediaWiki before 1.31.12 and 1.32.x through 1.35.x before 1.35.2. Special:Contributions can leak that a "hidden" user exists.

Record: BIT-mediawiki-2021-30156
Updated: 2026-11-02

Affected products

Affected packages

Affected packages
Package	Affected	Fixed
`mediawiki` Bitnami	before 1.31.12, 1.32.0 up to 1.35.2	1.31.121.35.2
`mediawiki` Ubuntu:18.04:LTS	All versions, plus listed versions 1:1.27.3-11:1.27.4-11:1.27.4-21:1.27.4-3	None known
`mediawiki` Ubuntu:Pro:20.04:LTS	All versions, plus listed versions 1:1.31.2-1ubuntu11:1.31.5-11:1.31.5-1ubuntu11:1.31.5-21:1.31.5-3 Show 4 moreShow less 1:1.31.5-3ubuntu11:1.31.6-11:1.31.7-11:1.31.7-1ubuntu0.1~esm1	None known
`mediawiki` Ubuntu:Pro:22.04:LTS	All versions, plus listed versions 1:1.35.3-11:1.35.4-11:1.35.5-11:1.35.5-1ubuntu11:1.35.5-1ubuntu21:1.35.5-1ubuntu31:1.35.6-11:1.35.6-1ubuntu0.1~esm1	None known
`mediawiki` Ubuntu:Pro:24.04:LTS	All versions, plus listed versions 1:1.39.4-21:1.39.5-11:1.39.6-11:1.39.7-11:1.39.7-1ubuntu0.1~esm1	None known
`mediawiki` Ubuntu:25.10	All versions, plus listed versions 1:1.43.1+dfsg-11:1.43.1+dfsg-21:1.43.3+dfsg-1	None known
`mediawiki` Ubuntu:26.10	All versions, plus listed versions 1:1.43.8+dfsg-21:1.43.9+dfsg-11:1.43.9+dfsg-1ubuntu1	None known
`mediawiki` Ubuntu:26.04:LTS	All versions, plus listed versions 1:1.43.3+dfsg-11:1.43.5+dfsg-11:1.43.6+dfsg-21:1.43.8+dfsg-11:1.43.8+dfsg-2	None known

History

History
Recorded	Changed	Sources
Nov 3, 2026	aliases	EUVD
Nov 2, 2026	first indexed	CVE List, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2021-30156 is a medium vulnerability (CVSS 4.3) in Mediawiki, published April 9, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 1.14%, the 66th percentile. Fixed in mediawiki 1.31.12.

References

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