Cloudreve: SSRF guard bypass: checkIP does not decode IPv6-transition wrappers (NAT64, IPv4-compatible, 6to4) reaching internal and cloud-metadata addresses

[ Description ]Official description

Cloudreve is a self-hosted file management and sharing system. Prior to 4.18.0, the ValidateExternalURL server-side request forgery guard in pkg/request/ssrf.go passes resolved addresses to checkIP without decoding NAT64, IPv4-compatible, and 6to4 IPv4-in-IPv6 transition forms. An authenticated user with remote-download access can provide SrcUri through RemoteDownloadTask.createDownloadTask so a wrapper embedding a loopback, private, link-local, or cloud metadata IPv4 address is classified as public and fetched, exposing internal service responses and cloud instance credentials. IPv4-mapped IPv6 addresses remain blocked because Go converts that form with net.IP.To4. This issue is fixed in version 4.18.0.

[ Fixes ]Fixes and patches

• github.com/cloudreve/Cloudreve/v4 4.0.0-20260715072853-1c5cad6dec7eFixed version · GitHub Advisories · go package github.com/cloudreve/Cloudreve/v4: upgrade to 4.0.0-20260715072853-1c5cad6dec7e or later (affected < 4.0.0-20260715072853-1c5cad6dec7e)

[ Packages ]Affected open-source packages

• github.com/cloudreve/Cloudreve/v4 goAffected < 4.0.0-20260715072853-1c5cad6dec7e · fixed in 4.0.0-20260715072853-1c5cad6dec7e · GHSA-jvh5-97xg-v99f

[ References ]References

• github.com/cloudreve/cloudreve/security/advisories/GHSA-jvh5-97xg-v99fx_refsource_CONFIRM
• github.com/cloudreve/cloudreve/commit/1c5cad6dec7ec3037c6479e3a26a3909995d16a2x_refsource_MISC
• github.com/cloudreve/cloudreve/releases/tag/4.18.0x_refsource_MISC