CVE-2021-31553
An issue was discovered in the CheckUser extension for MediaWiki through 1.35.2. MediaWiki...
An issue was discovered in the CheckUser extension for MediaWiki through 1.35.2. MediaWiki usernames with trailing whitespace could be stored in the cu_log database table such that denial of service occurred for certain CheckUser extension pages and functionality. For example, the attacker could turn off Special:CheckUserLog and thus interfere with usage tracking.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- None
- Integrity
- Low
- Availability
- Low
Exploit likelihood
What each source reports
NVD Score used
An issue was discovered in the CheckUser extension for MediaWiki through 1.35.2. MediaWiki usernames with trailing whitespace could be stored in the cu_log database table such that denial of service occurred for certain CheckUser extension pages and functionality. For example, the attacker could turn off Special:CheckUserLog and thus interfere with usage tracking.
- Record
CVE-2021-31553- CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L - CVSS 2.0
- 6.4 Medium
AV:N/AC:L/Au:N/C:N/I:P/A:P - Weakness
- CWE-428
- Updated
- 2026-11-02
CVE List No score
An issue was discovered in the CheckUser extension for MediaWiki through 1.35.2. MediaWiki usernames with trailing whitespace could be stored in the cu_log database table such that denial of service occurred for certain CheckUser extension pages and functionality. For example, the attacker could turn off Special:CheckUserLog and thus interfere with usage tracking.
- Record
CVE-2021-31553- Updated
- 2026-11-02
EUVDEUVD-2021-18450 No score
An issue was discovered in the CheckUser extension for MediaWiki through 1.35.2. MediaWiki usernames with trailing whitespace could be stored in the cu_log database table such that denial of service occurred for certain CheckUser extension pages and functionality. For example, the attacker could turn off Special:CheckUserLog and thus interfere with usage tracking.
- Record
EUVD-2021-18450- Updated
- 2026-11-03
GitHub AdvisoriesGHSA-6475-q4qm-387r No score
An issue was discovered in the CheckUser extension for MediaWiki through 1.35.2. MediaWiki...
An issue was discovered in the CheckUser extension for MediaWiki through 1.35.2. MediaWiki usernames with trailing whitespace could be stored in the cu_log database table such that denial of service occurred for certain CheckUser extension pages and functionality. For example, the attacker could turn off Special:CheckUserLog and thus interfere with usage tracking.
- Record
GHSA-6475-q4qm-387r- Weakness
- CWE-428
- Updated
- 2026-11-02
OSV
An issue was discovered in the CheckUser extension for MediaWiki through 1.35.2. MediaWiki usernames with trailing whitespace could be stored in the cu_log database table such that denial of service occurred for certain CheckUser extension pages and functionality. For example, the attacker could turn off Special:CheckUserLog and thus interfere with usage tracking.
- Record
CVE-2021-31553- CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L - Updated
- 2026-11-02
OSVBIT-mediawiki-2021-31553 No score
An issue was discovered in the CheckUser extension for MediaWiki through 1.35.2. MediaWiki usernames with trailing whitespace could be stored in the cu_log database table such that denial of service occurred for certain CheckUser extension pages and functionality. For example, the attacker could turn off Special:CheckUserLog and thus interfere with usage tracking.
- Record
BIT-mediawiki-2021-31553- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
mediawikiBitnami |
before 1.35.3 | 1.35.3 |
History
| Recorded | Changed | Sources |
|---|---|---|
| aliases | EUVD | |
| first indexed | CVE List, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2021-31553 is a medium vulnerability (CVSS 6.5) in Mediawiki, published April 22, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 1.40%, the 72nd percentile. Fixed in mediawiki 1.35.3.
References
phabricator.wikimedia.org/T275669
gerrit.wikimedia.org/r/c/mediawiki/extensions/CheckUser/+/667023
nvd.nist.gov/vuln/detail/CVE-2021-31553
github.com/advisories/GHSA-6475-q4qm-387r