Unauthenticated traffic forwarding via unchecked decapsulation
Published Jun 2, 2020 · Updated Nov 3, 2025
The IP-in-IP protocol in RFC 2003 allows remote attackers to route arbitrary network traffic through vulnerable devices. Devices decapsulate IPv4-in-IPv4 packets sent to local addresses without validating configured tunnel endpoints, then forward the inner packet while filtering checks the outer header. An unauthenticated attacker can exploit this remotely for access-control bypass, information disclosure, or reflective denial of service.
Summary
What happened
The IP-in-IP protocol in RFC 2003 allows remote attackers to route arbitrary network traffic through vulnerable devices. Devices decapsulate IPv4-in-IPv4 packets sent to local addresses without validating configured tunnel endpoints, then forward the inner packet while filtering checks the outer header. An unauthenticated attacker can exploit this remotely for access-control bypass, information disclosure, or reflective denial of service.
The record
- CVE
- CVE-2020-10136
- Published
- Jun 2, 2020
- Updated
- Nov 3, 2025
- Vendor
- Internet Engineering Task Force (IETF)
- Product
- RFC 2003: IP Encapsulation within IP
- Classifications
- CWE-19, T1090
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jun 2, 2020CVE publishedPublication date reported by the CVE source.
- Nov 3, 2025Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=STD 1
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Public exploit references
- CERTCC CVE-2020-10136 proof-of-conceptproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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