# Parse extended ICMP objects only after the original datagram and length fields > Use RFC 4884 — Extended ICMP to Support Multi-Part Messages to review this narrow operational decision without extending the source beyond its stated scope. - Canonical URL: https://update.dsesecurity.com/updates/parse-extended-icmp-objects-only-after-the-original-datagram-and-length-fields/ - Publisher: Detection Systems & Engineering (DSE Security) - Author: DSE Security Editorial Team - Published: 2026-08-27T12:16:19+00:00 - Modified: 2026-08-27T12:53:57+00:00 - Last reviewed by DSE: 2026-08-26 - Resource type: Checklist - DSE priority: Advisory - Topics: IT, Networks & Infrastructure - Reading time: 3 minutes ## What you need to know Use RFC 4884 — Extended ICMP to Support Multi-Part Messages to review this narrow operational decision without extending the source beyond its stated scope. ## Potentially affected Teams, systems, services, or facilities within the stated scope of RFC 4884 — Extended ICMP to Support Multi-Part Messages ## DSE recommendation Compare the observed state with the cited official source, document applicability and exceptions, and test any approved change with rollback safeguards. ## Article Treat this document as a focused evidence review: Parse extended ICMP objects only after the original datagram and length fields. Only the official source and traced locations below supply facts. Confirm applicability before acting. ## Source fact: The official [RFC 4884 — Extended ICMP to Support Multi-Part Messages](https://www.rfc-editor.org/rfc/rfc4884.html) from RFC Editor / Internet Engineering Task Force supports the following bounded statements: - The defined ICMPv4 and ICMPv6 error messages gain an original-datagram length field so an appended extension structure can be located after that field. The research record locates this support at Sections 3 (Summary of Changes to ICMP) and 4.1-4.5. - When extensions are present, the original-datagram field must contain at least 128 octets and be padded to a 32-bit boundary for ICMPv4 or a 64-bit boundary for ICMPv6. The research record locates this support at Section 3 (Summary of Changes to ICMP). - A receiver must validate message syntax and the extension checksum before processing extension objects; malformed lengths can otherwise cause buffer overruns. The research record locates this support at Section 9 (Security Considerations). Only the traced statements above are asserted as source facts. Apply the review to address plans, interfaces, routes, peers, protocol roles, timers, middleboxes, and intended failure domains after confirming that the source and deployed context match. ## What the source does not establish This RFC evidence supports only the named network-protocol decision; it does not select vendor settings, topology, capacity, or an acceptable failure mode. A correct source interpretation can still be inapplicable to a particular design. Confirm DNS, Active Directory authentication, PKI, time, routing policy, transport reachability, and monitoring, ownership, and change authority instead of treating documented behavior as a deployment guarantee. ## Applicability questions - For source statement 1 at Sections 3 (Summary of Changes to ICMP) and 4.1-4.5, which observable configuration, record, or test can confirm applicability here? - For source statement 2 at Section 3 (Summary of Changes to ICMP), which observable configuration, record, or test can confirm applicability here? - For source statement 3 at Section 9 (Security Considerations), which observable configuration, record, or test can confirm applicability here? - Within address plans, interfaces, routes, peers, protocol roles, timers, middleboxes, and intended failure domains, which versions, roles, and configuration states define the review population? - Could DNS, Active Directory authentication, PKI, time, routing policy, transport reachability, and monitoring invalidate the test, hide a failure, or change applicability? - Who owns the decision, and which observation requires stopping, escalation, or rollback? ## DSE recommendation: DSE recommends using the cited source as the evidence anchor for this decision. Begin by recording scope and current state before deciding whether a change is warranted. Record the source location, examined part of address plans, interfaces, routes, peers, protocol roles, timers, middleboxes, and intended failure domains, observed and expected states, owner, and reason for deviation. For an approved change, define prerequisites, a limited test path, success and stop conditions, monitoring, and rollback. Check DNS, Active Directory authentication, PKI, time, routing policy, transport reachability, and monitoring in design order. Protect credentials, keys, recovery material, personal data, and sensitive topology in evidence. ## Verification and evidence Build a reproducible chain from Sections 3 (Summary of Changes to ICMP) and 4.1-4.5; Section 3 (Summary of Changes to ICMP); Section 9 (Security Considerations) to the observed environment. Useful domain evidence includes configuration snapshots, route or neighbor state, packet captures, counters, topology records, and controlled failover results; label every item with scope, timestamp, collector, and stable identifier. Retain the starting state, authorization, execution record, outcome, deviation, and final state as one review package. Move disruptive checks to an approved test path. Reopen the decision when versions, design, dependencies, ownership, or official guidance changes. ## Official references - [RFC 4884 — Extended ICMP to Support Multi-Part Messages](https://www.rfc-editor.org/rfc/rfc4884.html) — RFC Editor / Internet Engineering Task Force ## Primary reference - Name: RFC 4884 — Extended ICMP to Support Multi-Part Messages - Authority: www.rfc-editor.org - URL: https://www.rfc-editor.org/rfc/rfc4884.html - Source publication date: Not stated by the source ## Citation and use Preferred citation: “Parse extended ICMP objects only after the original datagram and length fields,” DSE Security, https://update.dsesecurity.com/updates/parse-extended-icmp-objects-only-after-the-original-datagram-and-length-fields/ Publishing principles: https://update.dsesecurity.com/updates/dse-updates-editorial-methodology/ Usage and citation policy: https://update.dsesecurity.com/usage/ Copyright © 2026 Detection Systems & Engineering. All rights reserved.