Microsoft Windows
CVE-2019-1338 — Windows NTLM Security Feature Bypass Vulnerability
Executive Summary
A security feature bypass vulnerability exists in Microsoft Windows when a man-in-the-middle attacker is able to successfully bypass the NTLMv2 protection if a client is also sending LMv2 responses. An attacker who successfully exploited this vulnerability could gain the ability to downgrade NTLM security features. To exploit this vulnerability, the attacker would need to be able to modify NTLM traffic exchange. The update addresses the vulnerability by hardening NTLMv2 protection on the server-side.
Overview
5.9
CVSS MEDIUM
Important
MS Severity
Not Exploited
MS Exploit Status
N/A
MS Exploit Likelihood
CVSS Vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N/E:P/RL:O/RC:C
ATTACK VECTOR
Network
ATTACK COMPLEXITY
High
PRIVILEGES REQUIRED
None
USER INTERACTION
None
SCOPE
Unchanged
CONFIDENTIALITY
None
INTEGRITY
High
AVAILABILITY
None
EXPLOIT CODE MATURITY
Proof-of-Concept
REMEDIATION LEVEL
Official Fix
REPORT CONFIDENCE
Confirmed
Temporal Score: 4.8
EPSS Score
0.03319
probability of exploitation in the next 30 days
0.87311 percentile - updated 2026-07-25
View on FIRST.org
Known Exploits
No known exploits have been linked for this CVE yet. When available, exploit references will be sourced from public repositories and may be unverified, incomplete, or non-functional. Always review code carefully before use in any environment.
Acknowledgments
Yaron Zinar and Marina Simakov from Preempt
References
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