Critical severity · published Sep 29, 2026
CVE-2026-100240
TemplateSandbox does not check read permissions for the page being previewed
9.1
CVSS
0.3%
EPSS
No
On KEV
Description
Missing Authorization vulnerability in Wikimedia Foundation Mediawiki - TemplateSandbox Extension allows Accessing Functionality Not Properly Constrained by ACLs.
This issue affects Mediawiki - TemplateSandbox Extension: from * before 1.46.1, 1.45.5, 1.43.10.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
High
Integrity
High
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.3% · higher than 22% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
MT
Mediawiki - TemplateSandbox Extension · Wikimedia Foundation
before 1.46.1, 1.45.5, 1.43.10 · source: vendor
Affected product
MT
Mediawiki - TemplateSandbox Extension
Wikimedia Foundation
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-100240
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-100240
phabricator.wikimedia.org
https://phabricator.wikimedia.org/T407974
gerrit.wikimedia.org
https://gerrit.wikimedia.org/r/q/Iaf9f6e2280798af5516197257ddc0264b9ad9fb7
More from Mediawiki - TemplateSandbox Extension
4.8
CVE-2026-100376
TemplateSandbox can be abused for XSS by asking another user to preview a page with a certain sandbox prefix