CVE-2026-52769 YesWiki: Unauthenticated Server-Side Request Forgery via ActivityPub `Signature.keyId`
Unauthenticated attackers can trigger server-side requests to internal resources via ActivityPub keyId, enabling port scanning and metadata access.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-52769?
CVE-2026-52769 is a high-severity server-side request forgery vulnerability in yeswiki, published on 4 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
YesWiki is a wiki system written in PHP. From version 4.6.2 to before version 4.6.6, the POST /api/forms/{formId}/actor/inbox route - exposed publicly with acl:"public" - accepts an HTTP Signature header whose keyId parameter is a URL. HttpSignatureService::verifySignature() parses the header and immediately makes a server-side HTTP GET to that URL, before any cryptographic verification or URL validation. An unauthenticated remote attacker can therefore make YesWiki issue arbitrary outbound HTTP requests to any host the server can reach - internal services, cloud-metadata endpoints (169.254.169.254), intranet-only admin panels, etc. - and read enough back via timing and error-message oracles to scan ports, enumerate services, and (on a real cloud instance) reach IAM metadata. The only deployment-side precondition is that ActivityPub be enabled on at least one Bazar form. This issue has been patched in version 4.6.6.
Weakness: CWE-918
Which versions are affected by CVE-2026-52769?
2 open source packages ship an affected version, including yeswiki/yeswiki.
| Package | Affected | Fixed in |
|---|---|---|
yeswiki/yeswiki Packagist | From 4.6.2 | 4.6.6 |
yeswiki/yeswiki Packagist | From 4.6.2 | 4.6.6 |
How do I fix CVE-2026-52769?
Upgrade yeswiki/yeswiki to 4.6.6 or later.
Upgrade, and send outbound requests through an allow-list that blocks internal addresses. More about Server-side request forgery.
Is CVE-2026-52769 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-52769 exists.
Sources
Also known as GHSA-vw42-752g-5mrp.