CVE-2026-77609: Semantic MediaWiki has an open redirect in Special:URIResolver
Failure mode
Special:URIResolver resolves its user-controlled subpage to a MediaWiki title and issues an HTTP 303 redirect to $title->getFullURL() without validating the resolved target. A crafted subpage can make that target point off-host: an interwiki prefix redirects to the foreign wiki (for example Special:URIResolver/mw-3AFoo, which decodes to mw:Foo, redirects to https://www.mediawiki.org/wiki/Foo), and where the resolved URL carries an authority the target can even embed user:pass@host credentials. The result is an open redirect to an attacker-influenced host, usable for phishing from a trusted wiki URL.
Remediation
- The resolved target URL is parsed and compared against the current host at the redirect sink. - The redirect is rejected (bad-title error page) when a user or pass component is present, or when the host does not match the current host.
Maintenance note
Redirect code must validate the final target URL, not just the input path. Host comparison belongs at the redirect sink: each sink (special page, entry point) must validate its own target rather than relying on upstream normalisation.
Other sources
Semantic MediaWiki is a free, open-source extension to MediaWiki that lets users store and query data within the wiki's pages. Prior to version 7.2.0, Special:URIResolver resolves its user-controlled subpage to a MediaWiki title and issues an HTTP 303 redirect to $title->getFullURL() without validating the resolved target. A crafted subpage can make that target point off-host: an interwiki prefix redirects to the foreign wiki (for example Special:URIResolver/mw-3AFoo, which decodes to mw:Foo, redirects to https://www.mediawiki.org/wiki/Foo), and where the resolved URL carries an authority the target can even embed user:pass@host credentials. The result is an open redirect to an attacker-influenced host, usable for phishing from a trusted wiki URL. Version 7.2.0 fixes the issue.
— MITRE
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
composer/mediawiki/semantic-media-wikito a version that resolves this vulnerability.Fixed in 7.2.0 - Upgrade
Upgrade
Semantic MediaWiki (Special:URIResolver)to a version that resolves this vulnerability.Fixed in 7.2.0 - Configuration
Modify each redirect sink (e.g., Special page / entry point handler) to validate the final resolved target URL’s host (and disallow off-host/foreign-authority redirects) rather than relying on upstream normalization; validate the URL that will be used for the final HTTP 303 redirect.
Semantic MediaWiki / Special:URIResolver Validate resolved target URL at redirect sink = true
Event History
Frequently Asked Questions
Which deployments are affected?
Semantic MediaWiki deployments using Special:URIResolver are affected if they run a version earlier than 7.2.0. Version 7.2.0 fixes the issue.
What does an attacker need to exploit this?
An attacker only needs to get a victim to follow a crafted Special:URIResolver URL. The vector is network-accessible, requires no privileges, and requires user interaction.
How can the redirect be abused?
A crafted subpage can decode to an interwiki target and redirect users to a foreign wiki or another attacker-influenced host. The target URL may also include user:pass@host authority syntax, which can make phishing links appear more convincing.
How can I determine whether my instance is vulnerable?
Check the installed Semantic MediaWiki version: versions before 7.2.0 are affected. On an affected instance, Special:URIResolver requests whose subpage decodes to an interwiki-style title, such as mw:Foo, can produce an off-host HTTP 303 redirect.