Microsoft Windows NT 4.0 TCP Sequence Number authentication spoofing

CVSS Meta Temp Score
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Current Exploit Price (≈)
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CTI Interest Score
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A vulnerability was found in Microsoft Windows NT 4.0 (Operating System). It has been classified as critical. This affects an unknown part of the component TCP Sequence Number Handler. The manipulation with an unknown input leads to a weak authentication vulnerability. CWE is classifying the issue as CWE-290. This is going to have an impact on confidentiality. The summary by CVE is:

predictable tcp sequence numbers allow spoofing.

The weakness was published 01/01/1995 (Website). It is possible to read the advisory at This vulnerability is uniquely identified as CVE-1999-0077. The exploitability is told to be easy. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. Technical details are unknown but a public exploit is available. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 05/07/2019). Due to its background and reception, this vulnerability has a historic impact.

It is declared as highly functional. We expect the 0-day to have been worth approximately $25k-$100k. The vulnerability scanner Nessus provides a plugin with the ID 10443 (TCP/IP Predictable ISN (Initial Sequence Number) Generation Weakness), which helps to determine the existence of the flaw in a target environment. It is assigned to the family General and running in the context remote. The commercial vulnerability scanner Qualys is able to test this issue with plugin 82005 (Predictable TCP Initial Sequence Numbers Vulnerability).

Upgrading to version XP or 2000 eliminates this vulnerability.

The vulnerability is also documented in the databases at SecurityFocus (BID 107), X-Force (139), Secunia (SA8044), Vulnerability Center (SBV-520) and Tenable (10443). Similar entries are available at 14800, 16127, 16232 and 16233.





CPE 2.3infoedit

CPE 2.2infoedit


VulDB Meta Base Score: 5.3
VulDB Meta Temp Score: 5.1

VulDB Base Score: 5.3
VulDB Temp Score: 5.1
VulDB Vector: 🔍
VulDB Reliability: 🔍



VulDB Base Score: 🔍
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NVD Base Score: 🔍


Class: Weak authentication
CWE: CWE-290
ATT&CK: Unknown

Local: No
Remote: Yes

Availability: 🔍
Access: Public
Status: Highly functional

Price Prediction: 🔍
Current Price Estimation: 🔍


Nessus ID: 10443
Nessus Name: TCP/IP Predictable ISN (Initial Sequence Number) Generation Weakness
Nessus File: 🔍
Nessus Risk: 🔍
Nessus Family: 🔍
Nessus Context: 🔍

OpenVAS ID: 802266
OpenVAS Name: TCP/IP Predictable TCP Initial Sequence Number Vulnerability
OpenVAS File: 🔍
OpenVAS Family: 🔍

Qualys ID: 🔍
Qualys Name: 🔍

Threat Intelligenceinfoedit

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍


Recommended: Upgrade
Status: 🔍

0-Day Time: 🔍

Upgrade: Windows XP/2000


01/01/1995 🔍
01/01/1995 +0 days 🔍
01/01/1995 +0 days 🔍
06/30/1998 +1276 days 🔍
12/24/2002 +1638 days 🔍
03/03/2003 +69 days 🔍
06/17/2014 +4124 days 🔍
08/11/2017 +1151 days 🔍
05/07/2019 +634 days 🔍



Status: Confirmed

CVE: CVE-1999-0077 (🔍)
SecurityFocus: 107 - Portmaster Predictable TCP Initial Sequence Number Vulnerability
Secunia: 8044
X-Force: 139 - TCP sequence prediction
Vulnerability Center: 520 - Predictable TCP Sequence Number was Detected, Low

scip Labs:
See also: 🔍


Created: 06/17/2014 03:39 PM
Updated: 05/07/2019 09:44 AM
Changes: (2) source_securityfocus_date source_securityfocus_class
Complete: 🔍


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