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Vulnerability · Published Sep 4, 2026 · Assigned by GitHub_M

CVE-2026-52769YesWiki: Unauthenticated Server-Side Request Forgery via ActivityPub `Signature.keyId`

High 8.3

In plain English

A high-severity server-side request forgery in yeswiki from YesWiki. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 42% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)8.3High
Exploit odds (30 days)0.5%top 57.9% of all CVEs
Exploited in the wildNo reportsCISA SSVC: poc
Attack toolingNoneno public tooling known

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.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Packagistyeswiki/yeswiki4.6.6GHSA-vw42-752g-5mrp

Affected products (as reported)

VendorProductVersions
YesWiki yeswiki >= 4.6.2, < 4.6.6

Weakness: CWE-918 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:L

References