Microsoft Windows NT SP4-SP6 TCP sequence numbers are predictable
| nt-sequence-prediction-sp4 (3168) |  Medium Risk |
Description:
Microsoft Windows NT introduced a new method of generating TCP sequence numbers, designed to close a hole in previous versions of Windows NT. Earlier versions allowed these numbers to be easily guessed. However, it has been shown that systems using SP4 to SP6 are just as vulnerable to sequence number prediction attacks as earlier service packs.
Consequences:
Bypass Security
Remedy:
Apply the appropriate patch for your system, as listed in Microsoft Security Bulletin MS99-046, MS01-033, MS01-041, MS01-044 or MS02-018. See References.
The patch in MS99-046 significantly improves the randomness of the TCP initial sequence numbers (ISNs) generated by the TCP/IP stack in Microsoft Windows NT 4.0, providing 15 bits of entropy. Improving the randomness of ISNs eliminates a class of potential attacks against Windows NT 4.0 systems.
For Windows NT Server 4.0, Terminal Server Edition:
Microsoft originally provided a patch for this vulnerability in MS99-046, but it has been superseded by the patch released with MS01-033, which has been superseded by the patch released with MS02-018. See References.
For Windows NT 4.0:
Microsoft originally provided patches for this vulnerability in MS99-046, MS01-033, and MS01-041 but they have been superseded by the Security Roll-up patch released with MS02-001, and then superseded by the Security Roll-up patch released with MS02-018. See References.
For IIS:
Microsoft originally provided a patch for this vulnerability in MS01-033, but it has been superseded by the patch released with MS01-044 and 02-018, and then superseded by the patch released with MS03-018. See References.
For Windows 2000:
Microsoft originally provided a patch for this vulnerability in MS01-033, but it has been superseded by the patch released with MS02-001. See References.
References:
- BugTraq Mailing List, Tue, 24 Aug 1999 16:59:09 +0100: NT Predictable Initial TCP Sequence numbers - changes observed with SP4.
- CIAC Information Bulletin K-006: Microsoft - Improve TCP Initial Sequence Number Randomness.
- Microsoft Security Bulletin MS01-033: Unchecked Buffer in Index Server ISAPI Extension Could Enable Web Server Compromise.
- Microsoft Security Bulletin MS01-041: Malformed RPC Request Can Cause Service Failure.
- Microsoft Security Bulletin MS01-044: 15 August 2001 Cumulative Patch for IIS.
- Microsoft Security Bulletin MS02-001: Trusting Domains Do Not Verify Domain Membership of SIDs in Authorization Data.
- Microsoft Security Bulletin MS02-018: Cumulative Patch for Internet Information Services (Q319733).
- Microsoft Security Bulletin MS03-018: Cumulative Patch for Internet Information Service (811114).
- Microsoft Security Bulletin MS99-046: Patch Available to Improve TCP Initial Sequence Number Randomness.
- Microsoft Security Bulletin MS99-046 FAQ: Microsoft Security Bulletin MS99-046: Frequently Asked Questions.
- NTA Web site: Leading Security testers ¿NTA Monitor¿ Discover Security Flaw in Microsoft NT4 SP4.
- BID-604: NT Predictable TCP Sequence Number Vulnerability
- CVE-2000-0328: Windows NT 4.0 generates predictable random TCP initial sequence numbers (ISN), which allows remote attackers to perform spoofing and session hijacking.
Platforms Affected:
- Microsoft Windows 2000
- Microsoft Windows NT 3.5.1 SP5
- Microsoft Windows NT 3.5.1 SP4
- Microsoft Windows NT 4.0 SP6
- Microsoft Windows NT 4.0
- Microsoft Windows NT 4.0 Terminal Server
Reported:
Aug 25, 1999
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