How severe is CVE-2019-1166?

CVE-2019-1166 has a CVSS 3.x base score of 5.9, rated medium severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity high, and availability none.

Is CVE-2019-1166 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 62% (99th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2019-1166?

CVE-2019-1166 primarily affects Microsoft Windows 10. In total, 19 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2019-1166?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2019-1166 published?

CVE-2019-1166 was published on 2019-10-10 and last updated on 2026-06-17.

CVE-2019-1166

CVE-2019-1166 is a medium-severity vulnerability in Microsoft Windows 10 with a CVSS 3.x base score of 5.9. Its EPSS exploit-prediction score of 62% places it in the 99th percentile, indicating an elevated likelihood of exploitation. The underlying weakness is classified as CWE-354.

Key facts

Severity: Medium (CVSS 3.x base score 5.9)
CVSS v2: 4.3
EPSS exploit prediction: 62% (99th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-354
Affected product: Microsoft Windows 10
Published: 2019-10-10
Last modified: 2026-06-17

Description

A tampering vulnerability exists in Microsoft Windows when a man-in-the-middle attacker is able to successfully bypass the NTLM MIC (Message Integrity Check) protection, aka 'Windows NTLM Tampering Vulnerability'.

Frequently asked questions

What is CVE-2019-1166?: A tampering vulnerability exists in Microsoft Windows when a man-in-the-middle attacker is able to successfully bypass the NTLM MIC (Message Integrity Check) protection, aka 'Windows NTLM Tampering Vulnerability'.
How severe is CVE-2019-1166?: CVE-2019-1166 has a CVSS 3.x base score of 5.9, rated medium severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity high, and availability none.
Is CVE-2019-1166 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 62% (99th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2019-1166?: CVE-2019-1166 primarily affects Microsoft Windows 10. In total, 19 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2019-1166?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2019-1166 published?: CVE-2019-1166 was published on 2019-10-10 and last updated on 2026-06-17.

References

https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2019-1166

Affected products (19)

cpe:2.3:o:microsoft:windows_10:-:*:*:*:*:*:*:*
cpe:2.3:o:microsoft:windows_10:1607:*:*:*:*:*:*:*
cpe:2.3:o:microsoft:windows_10:1703:*:*:*:*:*:*:*
cpe:2.3:o:microsoft:windows_10:1709:*:*:*:*:*:*:*
cpe:2.3:o:microsoft:windows_10:1803:*:*:*:*:*:*:*
cpe:2.3:o:microsoft:windows_10:1809:*:*:*:*:*:*:*
cpe:2.3:o:microsoft:windows_10:1903:*:*:*:*:*:*:*
cpe:2.3:o:microsoft:windows_7:-:sp1:*:*:*:*:*:*
cpe:2.3:o:microsoft:windows_8.1:-:*:*:*:*:*:*:*
cpe:2.3:o:microsoft:windows_rt_8.1:-:*:*:*:*:*:*:*
cpe:2.3:o:microsoft:windows_server_2008:-:sp2:*:*:*:*:*:*
cpe:2.3:o:microsoft:windows_server_2008:r2:sp1:*:*:*:*:itanium:*
cpe:2.3:o:microsoft:windows_server_2008:r2:sp1:*:*:*:*:x64:*
cpe:2.3:o:microsoft:windows_server_2012:-:*:*:*:*:*:*:*
cpe:2.3:o:microsoft:windows_server_2012:r2:*:*:*:*:*:*:*
cpe:2.3:o:microsoft:windows_server_2016:-:*:*:*:*:*:*:*
cpe:2.3:o:microsoft:windows_server_2016:1803:*:*:*:*:*:*:*
cpe:2.3:o:microsoft:windows_server_2016:1903:*:*:*:*:*:*:*
cpe:2.3:o:microsoft:windows_server_2019:-:*:*:*:*:*:*:*

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