CVE-2026-126563 Semantic MediaWiki 2.4.0 before 7.4.1 Reflected XSS via Special:Ask Date Format
Unauthenticated attackers can craft Special:Ask URLs that run script in logged-in Semantic MediaWiki users' browsers.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Harmful if only installed
- No
- Needs a specific call
- No
- Fix
- None listed
What is CVE-2026-126563?
CVE-2026-126563 is a medium-severity cross-site scripting vulnerability in SemanticMediaWiki, published on 11 Nov 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
Semantic MediaWiki 2.4.0 before 7.4.1 contains a reflected cross-site scripting vulnerability in TimeValueFormatter::getCaptionFromFreeFormat(), which emits free-format date captions in HTML without escaping. Unauthenticated attackers can craft a Special:Ask URL with HTML markup in a date printout format (#-F[...]) to execute script in a logged-in victim's browser session.
Weakness: CWE-79
Which versions are affected by CVE-2026-126563?
An affected version is exposed as installed. No special setting or call is needed.
How do I fix CVE-2026-126563?
No fix has been published for CVE-2026-126563 yet. Limit exposure of the affected software until one is available.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-126563 being exploited?
There is no known exploitation of CVE-2026-126563 in the wild and no public exploit code.
Sources
Also known as GHSA-h252-mj7p-58q7, GHSA-p9g7-73wv-cwgh.