CVE-2026-113671: ApostropheCMS: Host header controls server-side image fetch origin in @apostrophecms/ai-helper, enabling authenticated SSRF
The @apostrophecms/ai-helper package builds the URL for a server-side image fetch by resolving a storage-relative path against req.baseUrl. When the site does not set a global base URL (the default), req.baseUrl is derived from the incoming HTTP Host header. An authenticated editor can generate a base64 AI image (which is persisted without a stored url) and then send an unauthorized PATCH accept request with an attacker-chosen Host header. The server then issues an outbound GET to the attacker-selected origin, producing a Server-Side Request Forgery primitive that reaches hosts and ports the client cannot otherwise contact. The affected code lives in packages/ai-helper/modules/@apostrophecms/ai-helper-image/index.js.
References
- github.com/advisories/GHSA-527g-ff96-x6wj
- github.com/apostrophecms/apostrophe/commit/9500b8b0e1d630d5e07fbb5fd2c25ed0943845ce
- github.com/apostrophecms/apostrophe/commit/f84fd41cbf6c22eb8d0008fc9c25df1f7130b350
- github.com/apostrophecms/apostrophe/releases/tag/@apostrophecms/ai-helper@1.0.0-beta.13
- github.com/apostrophecms/apostrophe/security/advisories/GHSA-527g-ff96-x6wj
- nvd.nist.gov/vuln/detail/CVE-2026-113671
Code Behaviors & Features
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