CAPEC-321
TCP Sequence Number Probe
This OS fingerprinting probe tests the target system's assignment of TCP sequence numbers. One common way to test TCP Sequence Number generation is to send a probe packet to an open port on the target and then compare the how the Sequence Number generated by the target relates to the Acknowledgement Number in the probe packet. Different operating systems assign Sequence Numbers differently, so a fingerprint of the operating system can be obtained by categorizing the relationship between the acknowledgement number and sequence number as follows: 1) the Sequence Number generated by the target is Zero, 2) the Sequence Number generated by the target is the same as the acknowledgement number in the probe, 3) the Sequence Number generated by the target is the acknowledgement number plus one, or 4) the Sequence Number is any other non-zero number.
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Explain the attack pattern CAPEC-321: TCP Sequence Number Probe: how it unfolds, what it needs and how to prevent and detect it in my systems. Use https://capec.mitre.org/data/definitions/321.html and https://cve.bz/cve/capec/321?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 monitor and interact with network communications.Access to at least one host, and the privileges to interface with the network interface card.
Resources required
A tool capable of sending and receiving packets from a remote system.
Consequences
| Impact | Affects | Note |
|---|---|---|
| Read Data | Confidentiality | |
| Bypass Protection Mechanism, Hide Activities | Confidentiality, Access Control, Authorization |
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-312 Active OS Fingerprinting
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