CVE-2026-100240 TemplateSandbox does not check read permissions for the page being previewed
Attackers can bypass access controls to view restricted pages via the TemplateSandbox extension in MediaWiki.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-100240?
CVE-2026-100240 is a critical missing authorization vulnerability in Wikimedia Foundation Mediawiki - TemplateSandbox Extension, published on 29 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Weakness: CWE-862
Which versions are affected by CVE-2026-100240?
How do I fix CVE-2026-100240?
No fix has been published for CVE-2026-100240 yet. Limit exposure of the affected software until one is available.
Upgrade, and check permissions on every request on the server, not only in the interface. More about Missing authorization.
Is CVE-2026-100240 being exploited?
There is no known exploitation of CVE-2026-100240 in the wild and no public exploit code.
Sources
Also known as GHSA-3835-4xp5-hjqc.