CAPEC-297
TCP ACK Ping
An adversary sends a TCP segment with the ACK flag set to a remote host for the purpose of determining if the host is alive. This is one of several TCP 'ping' types. The RFC 793 expected behavior for a service is to respond with a RST 'reset' packet to any unsolicited ACK segment that is not part of an existing connection. So by sending an ACK segment to a port, the adversary can identify that the host is alive by looking for a RST packet. Typically, a remote server will respond with a RST regardless of whether a port is open or closed. In this way, TCP ACK pings cannot discover the state of a remote port because the behavior is the same in either case. The firewall will look up the ACK packet in its state-table and discard the segment because it does not correspond to any active connection. A TCP ACK Ping can be used to discover if a host is alive via RST response packets sent from the host.
On this page
Ask an AI about this attack pattern
Show the prompt
Explain the attack pattern CAPEC-297: TCP ACK Ping: how it unfolds, what it needs and how to prevent and detect it in my systems. Use https://capec.mitre.org/data/definitions/297.html and https://cve.bz/cve/capec/297?via=ask-ai-copy, which lists recent CVEs with the weaknesses it exploits. Cite the sources.Opens a third-party assistant; its answer is its own, not cve.bz's. The prompt holds only this attack pattern's id and public links.
Prerequisites
The ability to send an ACK packet to a remote host and identify the response. Creating the ACK packet without building a full connection requires the use of raw sockets. As a result, it is not possible to send a TCP ACK ping from some systems (Windows XP SP 2) without the use of third-party packet drivers like Winpcap. On other systems (BSD, Linux) administrative privileges are required in order to write to the raw socket.
The target must employ a stateless firewall that lacks a rule set that rejects unsolicited ACK packets.
The adversary requires the ability to craft custom TCP ACK segments for use during network reconnaissance. Sending an ACK ping requires the ability to access "raw sockets" in order to create the packets with direct access to the packet header.
Resources required
ACK scanning can be performed via the use of a port scanner or by raw socket manipulation using a scripting or programming language. Packet injection tools are also useful for this purpose. Depending upon the technique used it may also be necessary to sniff the network in order to see the response.
Consequences
| Impact | Affects | Note |
|---|---|---|
| Other | Confidentiality | |
| Bypass Protection Mechanism, Hide Activities | Confidentiality, Access Control, Authorization |
Mitigations
Leverage stateful firewalls that allow for the rejection of a packet that is not part of an existing connection.
Weaknesses it exploits
- CWE-200 Exposure of Sensitive Information to an Unauthorized Actor
Recent CVEs with these weaknesses
- 4.3CVE-2026-124944
Information disclosure in the Marionette component. This vulnerability was fixed in Firefox 160.
- 4.3CVE-2026-124941
Information disclosure in the Security: RLBox component. This vulnerability was fixed in Firefox 160 and Firefox ESR 153.7.
- 4.3CVE-2026-124930
Information disclosure in the Address Bar component. This vulnerability was fixed in Firefox 160 and Firefox ESR 153.7.
- 4.3CVE-2026-124929
Information disclosure in the Layout: Form Controls component. This vulnerability was fixed in Firefox 160 and Firefox ESR 153.7.
- 4.3CVE-2026-124925
Information disclosure in the Layout component. This vulnerability was fixed in Firefox 160.
- 4.3CVE-2026-124909
Information disclosure in the Private Browsing component. This vulnerability was fixed in Firefox 160 and Firefox ESR 153.7.
- 5.3CVE-2026-96769
The Extend B2B - Companies and Users Management for WooCommerce plugin for WordPress is vulnerable to Sensitive Information Exposure in all versions up to, and including, 2.1.4 via the register_company_api. This makes it possible for unaut…
- 7.5CVE-2026-63644
bird-lg-go is a BIRD looking glass in Go. Prior to version 1.4.7, unsanitized input path enables arbitrary local file read, allowing an unauthenticated remote attacker to read sensitive files such as /etc/shadow and /root/.bash_history. Th…
The newest records naming one of them. Each weakness's page lists them all.
Related attack patterns
- Part of
- CAPEC-292 Host Discovery
MITRE's words, unchanged: CAPEC-297 at MITRE. CAPEC is Copyright © 2007–2026, The MITRE Corporation, used under the CAPEC terms of use: “The MITRE Corporation (MITRE) hereby grants you a non-exclusive, royalty-free license to use Common Attack Pattern Enumeration and Classification (CAPEC™) for research, development, and commercial purposes. Any copy you make for such purposes is authorized provided that you reproduce MITRE’s copyright designation and this license in any such copy.” CAPEC and the CAPEC logo are trademarks of The MITRE Corporation. Credits. All attack patterns.