CWE-294: Authentication Bypass by Capture-replay
A capture-replay flaw exists when the design of the product makes it possible for a malicious user to sniff network traffic and bypass authentication by replaying it to the server in question to the same effect as the original message (or with minor changes).
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Overview
Capture-replay attacks are common and can be difficult to defeat without cryptography. They are a subset of network injection attacks that rely on observing previously-sent valid commands, then changing them slightly if necessary and resending the same commands to the server.
Real-world CVEs
139 recorded CVEs are caused by CWE-294 (Authentication Bypass by Capture-replay). The highest-severity and most recent are shown first. 22 new CWE-294 CVEs have been recorded so far in 2026 (23 in 2025).