Source: CQURE Academy
Author: Kate Chrzan
URL: https://cqureacademy.com/blog/65-ntlm-reflection-smb-flaw/
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ONE SENTENCE SUMMARY: CVE-2025-33073 enables attackers to exploit legacy SMB protocols and coercion methods for full system compromise via NTLM relay.
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MAIN POINTS:
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SMB signing must be disabled on the target machine to allow authentication relay attacks.
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The target must be vulnerable to coercion techniques like PetitPotam for exploitation to proceed.
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Initial attack attempts without a DNS record fail due to inability to authenticate properly.
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Adding a DNS record pointing to the attacker’s machine enables successful NTLM relay and SAM dump.
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Changing the IP to the DNS record value allows the machine to relay authentication to itself.
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LLMNR poisoning via Responder enables attacks without needing the DNS record.
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Using impacket-ntlmrelayx with netexec and coerce_plus exploits the PrinterBug vulnerability.
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Successful execution allows retrieval of local admin hash and local authentication.
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Module LSA from netexec can be used to dump LSASS and gain further access.
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The vulnerability highlights critical risks from legacy authentication protocols and misconfigurations.
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TAKEAWAYS:
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Disable SMB signing only if absolutely necessary, as it allows dangerous relay attacks.
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Monitor and restrict DNS records to prevent abuse in authentication redirection.
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Employ modern authentication mechanisms to mitigate legacy protocol exploitation.
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Use tools like Responder and PetitPotam carefully during red team engagements or internal audits.
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Regularly update systems and audit for coercion vulnerabilities like PrinterBug.