User Enumeration Vulnerability in OpenSSH by The OpenBSD Foundation

CVE-2016-6210

Summary

In OpenSSH versions prior to 7.3, an exposure exists where the password hashing mechanism, utilizing SHA256 or SHA512, falls back to BLOWFISH hashing when attempting to authenticate a non-existent username. This flaw creates a timing discrepancy in the responses to authentication requests, potentially enabling remote attackers to enumerate valid usernames based on the observed timing of responses when large passwords are input. Such an exploit can facilitate further intrusion attempts against targeted systems.

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