A vulnerability was found in kkFileView 4.4.0. It has been classified as critical. This affects an unknown part of the file /fileUpload. The manipulation of the argument File leads to unrestricted upload. It is possible to initiate the attack remotely. The exploit has been disclosed to the public and may be used. The vendor was contacted early about this disclosure but did not respond in any way.

kkFileView is a universal file online preview project based on Spring Boot. Prior to 5.0.1, the unauthenticated GET /addTask endpoint in kkFileView is omitted from TrustHostFilter and TrustDirFilter in server/src/main/java/cn/keking/config/WebConfig.java, allowing FileConvertQueueTask to fetch an attacker-selected URL after FileHandlerService#getFileAttribute uses the fullfilename parameter to force an OFFICE, COMPRESS, or CAD type. This issue is fixed in version 5.0.1.

kkFileView 5.0.0 through 5.0.2 allows reflected XSS via the /onlinePreview endpoint. The OnlinePreviewController passes the user-controlled page and kkagent request parameters to FreeMarker templates without sanitization, and the templates insert these values into raw JavaScript contexts.

kkFileView >= 4.2.0 is vulnerable to Server-Side Request Forgery (SSRF). The cross-origin file proxy endpoint /getCorsFile is protected by TrustHostFilter against the trust.host whitelist. However, the URL parameter validated by the filter is not the same parameter the controller actually fetches: the filter validates the first non-empty parameter in a fixed priority order, while the controller only reads and fetches urlPath. By supplying both urlPath=<real target> and url=<whitelisted decoy address> in the same request, the decoy passes validation while the unvalidated real target is fetched server-side — and the response body is echoed back to the attacker.