Description

Misskey is an open source, decentralized social media platform with ActivityPub support. Prior to version 2024.2.0, when fetching remote Activity Streams objects, Misskey doesn't check that the response from the remote server has a `Content-Type` header value of the Activity Streams media type, which allows a threat actor to upload a crafted Activity Streams document to a remote server and make a Misskey instance fetch it, if the remote server accepts arbitrary user uploads. The vulnerability allows a threat actor to impersonate and take over an account on a remote server that satisfies all of the following properties: allows the threat actor to register an account; accepts arbitrary user-uploaded documents and places them on the same domain as legitimate Activity Streams actors; and serves user-uploaded document in response to requests with an `Accept` header value of the Activity Streams media type. Version 2024.2.0 contains a patch for the issue.

Weaknesses 1

Affected Products 1

References 5

• github.com https://github.com/misskey-dev/misskey/blob/2024.2.0-beta.10/packages/backend/src/core/activitypub/ApResolverService.ts#L69-L119
  Product
• github.com https://github.com/misskey-dev/misskey/blob/2024.2.0-beta.10/packages/backend/src/core/activitypub/models/ApNoteService.ts#L112-L308
  Product
• github.com https://github.com/misskey-dev/misskey/blob/2024.2.0-beta.10/packages/backend/src/server/api/endpoints/ap/show.ts#L125-L143
  Product
• github.com https://github.com/misskey-dev/misskey/commit/9a70ce8f5ea9df00001894809f5ce7bc69b14c8a
  Patch
• github.com https://github.com/misskey-dev/misskey/security/advisories/GHSA-qqrm-9grj-6v32
  Vendor Advisory

Remediation

• github.com https://github.com/misskey-dev/misskey/commit/9a70ce8f5ea9df00001894809f5ce7bc69b14c8a
  Patch