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Vulnerability record · CVE-2026-52769 · published 5 September 2026

CVE-2026-52769: Server-side request forgery (SSRF) vulnerability

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.

8.3 CVSS 3.1 High EPSS 0.49% · top 60.6% CWE-918 · Server-side request forgery (SSRF) Deferred
8.3CVSS 3.1 base score
0.49%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
4References
8 Sep 2026Last modified by NVD

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.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:L

References

LinkTags
http://github.com/YesWiki/yeswiki/commit/87e627f33e79879827a3669fee2aa1244612c487
https://github.com/YesWiki/yeswiki/releases/tag/v4.6.6
https://github.com/YesWiki/yeswiki/security/advisories/GHSA-vw42-752g-5mrp
https://github.com/YesWiki/yeswiki/security/advisories/GHSA-vw42-752g-5mrp

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Source: NIST National Vulnerability Database (record CVE-2026-52769), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.