PT-2026-45014 · Go · Github.Com/Gotenberg/Gotenberg/V8

Published

2026-05-29

·

Updated

2026-05-29

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CVE-2026-45741

CVSS v3.1

7.5

High

VectorAV:N/AC:H/PR:N/UI:N/S:C/C:H/I:L/A:N

Summary

IsPublicIP in pkg/gotenberg/outbound.go incorrectly classifies IPv6 6to4 / NAT64 / deprecated site-local addresses as public IPs, allowing an unauthenticated attacker to reach internal destinations (e.g., cloud metadata services at 169.254.169.254) via a single crafted DNS AAAA record. This is a variant of CVE-2026-44430 (modelcontextprotocol/registry).

Details

IsPublicIP uses Go stdlib helpers (IsLoopback, IsPrivate, IsLinkLocalUnicast, etc.) to block internal IPs. However, these helpers do not recognize IPv6 prefixes that embed IPv4 addresses:
PrefixRFCTunnels to
2002::/16RFC 3056 (6to4)IPv4 in bits 16-47
64:ff9b::/96RFC 6052 (NAT64 well-known)IPv4 in low 32 bits
64:ff9b:1::/48RFC 8215 (NAT64 local-use)IPv4 in low 32 bits
fec0::/10RFC 3879 (deprecated site-local)internal routing
addr.Unmap() only handles ::ffff:0:0/96 (IPv4-mapped) and has no effect on these prefixes. On dual-stack or NAT64-enabled cloud hosts, the OS kernel transparently routes these addresses to their embedded internal IPv4 destinations.
Vulnerable code (pkg/gotenberg/outbound.go L53-69, commit 93d0103):
func IsPublicIP(addr netip.Addr) bool {
  addr = addr.Unmap() // only handles ::ffff:x.x.x.x
  switch {
  case addr.IsLoopback(), addr.IsPrivate(),
     addr.IsLinkLocalUnicast(), ...:
    return false
  }
  return true // 6to4/NAT64/site-local incorrectly reaches here
}

PoC

cd poc/
./build.sh  # docker build (~30s)
./run.sh   # docker run — exits with code 1 (bug detected)
Expected output: IsPublicIP(2002:a9fe:a9fe::) = true — the function returns true for 3 addresses that wrap 169.254.169.254 (AWS IMDS). Full test file available via GHSA private comment on request.

Impact

An unauthenticated attacker controlling a DNS AAAA record can tunnel gotenberg's outbound HTTP client to AWS/GCP/Azure IMDS (169.254.169.254), leaking IAM credentials. The Chromium URL convert route returns the full response as a PDF (full-read SSRF). Affects all deployments with WithDenyPrivateIPs(true) on dual-stack or NAT64-enabled hosts.

Suggested Fix

Add explicit prefix checks after addr.Unmap():
var blockedIPv6Prefixes = []netip.Prefix{
  netip.MustParsePrefix("2002::/16"),
  netip.MustParsePrefix("64:ff9b::/96"),
  netip.MustParsePrefix("64:ff9b:1::/48"),
  netip.MustParsePrefix("fec0::/10"),
}
for , p := range blockedIPv6Prefixes {
  if p.Contains(addr) { return false }
}

Fix

SSRF

Incomplete List of Disallowed Inputs

Weakness Enumeration

CWE-918CWE-184

Related Identifiers

CVE-2026-45741
GHSA-86M8-88FQ-XFXP

Affected Products

Github.Com/Gotenberg/Gotenberg/V8