What is CVE-1999-0994?

CVE-1999-0994 is a vulnerability in Microsoft Windows Nt, classified under CWE-255. Published 1999-12-16.

Is CVE-1999-0994 known to be exploited?

1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.

Vulnerability in Microsoft Windows Nt

CVE-1999-0994

Windows NT with SYSKEY reuses the keystream that is used for encrypting SAM password hashes, allowing an attacker to crack passwords.

Published 1999-12-16 · last modified 2026-06-16.

CVSS v2 metric

CVSS v2 base score 5.0 (Medium). Vector: AV:N/AC:L/Au:N/C:P/I:N/A:N. This CVE predates CVSS v3 and has no v3 score from NVD.

EPSS exploit prediction

EPSS: 0.071 (94.1th percentile), scored 2026-09-29.

Low probability of exploitation in the next 30 days, but still tracked. 94th percentile — 94.1% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.072 · newest: 0.071 · change: -0.001

Affected products

Microsoft Windows Nt — versions 4.0

Weakness classification (CWE)

CWE-255

Public proof-of-concept exploits

ARPSyndicate/cve-scores

References

www.securityfocus.com/bid/873 (vdb-entry)
support.microsoft.com/default.aspx (vendor-advisory)
docs.microsoft.com/en-us/security-updates/securitybulletins/1999/ms99-056 (vendor-advisory)

Frequently asked questions

What is CVE-1999-0994?: CVE-1999-0994 is a vulnerability in Microsoft Windows Nt, classified under CWE-255. Published 1999-12-16.
Is CVE-1999-0994 known to be exploited?: 1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.