dbcve.org
Ipv6Application · Ietf

CVE-2025-23018

MEDIUM · 6.5 CVSS v3.1 Published 2025-01-14
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
74/100
Remediation priority · Elevated
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
IPv4-in-IPv6 and IPv6-in-IPv6 tunneling (RFC 2473) do not require the validation or verification of the source of a network packet, allowing an attacker to spoof and route arbitrary traffic via an exposed network interface. This is a similar issue to CVE-2020-10136.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

This vulnerability exists in IPv4-in-IPv6 and IPv6-in-IPv6 tunnel implementations (RFC 2473) where the receiving endpoint does not validate or verify the source of tunneled packets. An attacker can spoof arbitrary traffic and route it through an exposed tunnel interface, potentially bypassing network segmentation and firewall rules that only inspect the outer IPv6 header.

MitigationDisable unused tunnel interfaces, implement strict firewall rules allowing tunnel traffic only from known legitimate endpoints, and consider implementing IPsec AH/ESP for authentication of tunnel traffic.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Ipv6Application
Affected:all versions

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
High
Privileges
None
User interaction
None
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
Low

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:L

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify IPv6 tunnel interfaces
    List all network interfaces using 'ip link show' (Linux), 'netsh interface show' (Windows), or 'ifconfig -a' (Unix). Look for tunnel interfaces with names like 'sit', 'ip6tnl', 'tun', 'tap', or interfaces with 'tunnel' in the description.
    Affected if Any IPv6 tunnel interface (IPv4-in-IPv6 or IPv6-in-IPv6) exists on the system
  2. Confirm tunnel type
    Use 'ip -6 tunnel show' (Linux) or examine interface details to determine if tunnels are configured as sit (IPv4-in-IPv6), ip6ip6 (IPv6-in-IPv6), or ip6tnl (dynamic). Check tunnel configuration files or running config for tunnel mode.
    Affected if Tunnel mode is set to 'ip6ip6', 'sit', 'ip6tnl', or any RFC 2473 compliant tunnel mode
  3. Check firewall rules for outer header only
    Review firewall rules (iptables, nftables, pf, Windows Firewall) for inbound tunnel traffic. Look for rules that accept traffic on the tunnel interface or IPv6 protocol without inspecting the inner (encapsulated) packet source address.
    Affected if Firewall allows IPv6 tunnel traffic based solely on the outer IPv6 header without validating the inner packet source
  4. Verify source validation on tunnel endpoints
    Examine tunnel configuration for source validation. On Linux, check for 'ip6tnl' with 'local' and 'remote' endpoints explicitly defined. Look for any anti-spoofing measures or input validation on the tunnel interface.
    Affected if Tunnel accepts packets from any remote endpoint without validating that the source matches the configured remote address
  5. Check for IPsec protection on tunnels
    Review IPsec policies using 'ip xfrm policy show' (Linux) or equivalent. Verify if AH (Authentication Header) or ESP (Encapsulating Security Payload) is configured for the tunnel traffic to provide source authentication.
    Affected if No IPsec AH or ESP authentication is configured for the tunnel interface and tunnel traffic is not cryptographically protected

The system is affected if IPv6 tunnel interfaces (IPv4-in-IPv6 or IPv6-in-IPv6) exist and the firewall or tunnel configuration does not validate source addresses of encapsulated packets or use IPsec authentication.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Disable unused tunnel interfaces, implement strict firewall rules allowing tunnel traffic only from known legitimate endpoints, and consider implementing IPsec AH/ESP for authentication of tunnel traffic.

Fix this in Ipv6 Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA4.0 h
22.0 hours of engineering $3,860
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2025-23018 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
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  • Version or environment caveats, and links to real fixes
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