Detect CVE-2026-46595: golang.org/x/crypto/ssh VerifiedPublicKeyCallback Authentication Bypass in Elastic Security
Detects exploitation of CVE-2026-46595, a critical authentication bypass vulnerability (CVSS 10.0) in golang.org/x/crypto/ssh versions prior to 0.52.0. When VerifiedPublicKeyCallback is used, SSH server implementations fail to enforce permission checks, allowing attackers to authenticate without proper authorization. This is a regression/variant of CVE-2024-45337 and carries a public PoC.
MITRE ATT&CK
Elastic Detection Query
sequence by host.name with maxspan=5m
[authentication where
event.action in ("ssh_login", "user_login", "authenticated") and
event.outcome == "success" and
(
process.name in ("sshd", "ssh") or
user_agent.original like~ "*golang*" or
user_agent.original like~ "*crypto/ssh*"
) and
authentication.type == "publickey"
] by source.ip, user.name
[network where
network.protocol == "ssh" and
event.action == "connection_attempted" and
source.ip != "127.0.0.1"
] by source.ip, user.nameEQL sequence detection for CVE-2026-46595 that correlates successful SSH public key authentication with subsequent network connections, identifying potential authentication bypass exploitation on Go-based SSH servers.
Data Sources
Required Tables
False Positives & Tuning
- Authorized users performing SSH key-based logins followed by legitimate network activity
- Automated deployment and configuration management tools using SSH public key auth
- Security scanning tools performing authenticated SSH checks against managed hosts
- DevOps workflows involving SSH tunneling and port forwarding for development
Other platforms for CVE-2026-46595
Testing Methodology
Validate this detection against 3 adversary techniques from Atomic Red Team. Each test below lists the behaviour to exercise and the telemetry you should expect to see. Executable commands and cleanup steps are available with Pro.
- Test 1CVE-2026-46595 PoC: VerifiedPublicKeyCallback Auth Bypass Simulation
Expected signal: SSH authentication log entry showing 'Accepted publickey for testuser' despite the key not being in the authorized_keys list or having required permissions. Process execution events showing 'id', 'hostname', and echo commands as child processes of the SSH daemon.
- Test 2Identify Vulnerable golang.org/x/crypto/ssh Deployments via Binary Inspection
Expected signal: Process execution events for 'go' binary with 'version -m' arguments, file access events on Go binaries in /usr/local/bin, /usr/bin, /opt, and /proc/*/exe paths.
- Test 3SSH Brute-Force Simulation Against Go SSH Server to Test Alerting
Expected signal: Multiple 'Invalid user' or 'Failed publickey' log entries from the lab host IP, followed by potential 'Accepted publickey' entries if testing against a vulnerable server. Network connection events on the SSH port from the test machine.
References (7)
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