CVE-2026-57448: Blombooru: administrator image-proxy server-side request forgery
Blombooru is a self-hosted personal booru for organizing and tagging private image collections. Prior to 1.40.0, the administrator-only GET /proxy-image endpoint, exposed as /api/booru-import/proxy-image, accepts a url query parameter and fetches it server-side without meaningful destination validation. proxyimage() in backend/app/routes/booruimport.py only checks whether the value starts with http, then uses getclientforurl or requests.get and streams the response. Private, loopback and link-local addresses are not blocked, and automatically followed redirects can move a request from a trusted domain to an internal address. An authenticated administrator can enumerate internal services and access cloud instance metadata, potentially disclosing IAM credentials and crossing the application's intended cloud or network trust boundary. The reporter also observed a hanging recursive self-request. Administrator authentication remains a prerequisite; this is not an anonymous proxy. This issue is fixed in version 1.40.0.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
Blombooruto a version that resolves this vulnerability.Fixed in 1.40.0
Event History
Frequently Asked Questions
Who can exploit this issue?
Exploitation requires authentication as a Blombooru administrator. It is not an anonymous proxy vulnerability, but any administrator account can cause the server to make requests to internal, loopback, link-local, or redirected internal destinations.
Are default deployments affected?
Affected versions expose the vulnerable administrator-only proxy endpoint and do not meaningfully validate request destinations. The impact depends on what services or cloud metadata endpoints the Blombooru server can reach from its network environment.
What can an attacker do with administrator access?
They can use the server to enumerate reachable internal services and request cloud instance metadata. This may disclose IAM credentials and allow requests across the application's intended network or cloud trust boundary.
What should be done if upgrading is not immediately possible?
Restrict administrator access and prevent the Blombooru host from reaching unnecessary internal, loopback, link-local, and cloud metadata services. This reduces the destinations available through the proxy endpoint until version 1.40.0 can be deployed.
How can I determine whether my deployment is affected?
Deployments running versions prior to 1.40.0 are affected. The relevant administrator endpoint is GET /api/booru-import/proxy-image, which accepts a url query parameter.