Cloudreve: SSRF guard bypass: checkIP does not decode IPv6-transition wrappers (NAT64, IPv4-compatible, 6to4) reaching internal and cloud-metadata addresses
**Summary** Cloudreve's server-side request forgery guard `ValidateExternalURL` (`pkg/request/ssrf.go`) resolves a user-supplied URL host and rejects it when any resolved IP is a loopback, private, link-local, multicast, unspecified, CGNAT, or the cloud-metadata address. The classification is performed by `checkIP`, which uses Go's `net.IP` builtins (`IsLoopback`, `IsPrivate`, `IsLinkLocalUnicast`, ...) directly on the resolved address. These builtins inspect only the outer IPv6 address and do not decode IPv4-in-IPv6 transition wrappers. An attacker who controls a hostname's AAAA record (or, on a DNS64/NAT64 network, any hostname) can point the remote-download URL at a NAT64 well-known-prefix address (`64:ff9b::a.b.c.d`, RFC 6052), an IPv4-compatible address (`::a.b.c.d`, RFC 4291), or a 6to4 address (`2002:AABB:CCDD::`, RFC 3056) that wraps an internal IPv4. Go classifies these wrappers as ordinary global IPv6 addresses, so `checkIP` accepts them; the network then delivers the request to the embedded internal IPv4 (loopback, RFC 1918, or the cloud instance metadata service `169.254.169.254`). This bypasses the SSRF guard that was added to block direct access to internal services. **Affected component and versions** - Component: `pkg/request/ssrf.go` (`ValidateExternalURL` / `checkIP`), reached from the remote-download workflow `pkg/filemanager/workflows/remote_download.go` (`RemoteDownloadTask.createDownloadTask`, which passes the user-supplied `SrcUri` to `ValidateExternalU
GHSA-jvh5-97xg-v99f
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: osv:GHSA-jvh5-97xg-v99f
github.com/cloudreve/Cloudreve/v4
Source reference: /affected/0/package/name
- Affected versions
- Not stated in this record
- Fixed versions
- 4.0.0-20260715072853-1c5cad6dec7e
Source reference:
/affected/0/ranges - Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"ranges": [
{
"type": "SEMVER",
"events": [
{
"introduced": "0"
},
{
"fixed": "4.0.0-20260715072853-1c5cad6dec7e"
}
]
}
],
"package": {
"name": "github.com/cloudreve/Cloudreve/v4",
"purl": "pkg:golang/github.com/cloudreve/Cloudreve/v4",
"ecosystem": "Go"
},
"database_specific": {
"source": "https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/09/GHSA-jvh5-97xg-v99f/GHSA-jvh5-97xg-v99f.json"
}
}
]- Related CVEs
- CVE-2026-79913
Source reference:
/aliases
Publisher severity
No explicit severity was provided.
- Event
- #63925 · Revision 1
- Added to Heist Feed
- Publisher date