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Terminal ServerApplication · Microsoft

CVE-1999-0909

HIGH · 7.5 CVSS v2.0 Published 1999-09-20
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Multihomed Windows systems allow a remote attacker to bypass IP source routing restrictions via a malformed packet with IP options, aka the "Spoofed Route Pointer" vulnerability.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · moderate confidence

This vulnerability in multihomed Windows systems allows remote attackers to bypass IP source routing restrictions by sending malformed packets with crafted IP options. The 'Spoofed Route Pointer' flaw exploits how Windows processes IP option fields, enabling an attacker to circumvent routing controls and potentially redirect network traffic through malicious paths.

MitigationApply available Microsoft patches for this vulnerability; if patches are unavailable for legacy systems, disable IP source routing at the network perimeter or via registry settings to block potentially malicious source-routed packets.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Terminal ServerApplication
Affected:all versions
Windows 95Operating system
Affected:= 0a= 0b
Windows 98seOperating system
Affected:all versions
Windows NtOperating system
Affected:= 4.0

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Authentication
None
Confidentiality
Partial
Integrity
Partial
Availability
Partial

AV:N/AC:L/Au:N/C:P/I:P/A:P

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify Windows version
    Run 'winver' or check System Properties to determine the exact Windows version and build number
    Affected if The system is running Microsoft Terminal Server (any version), Windows 95 builds 0a or 0b, Windows 98se (any version), or Windows NT version 4.0
  2. Check IP source routing configuration
    Examine the registry key HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Tcpip\Parameters\IPSourceRouting or check via network adapter TCP/IP properties
    Affected if IP source routing is set to 'Enabled' or a value that permits source-routed packets (typically value 2 or higher)

A system is affected if it runs one of the specified Windows versions AND has IP source routing enabled, allowing malicious source-routed packets to bypass routing restrictions.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Apply available Microsoft patches for this vulnerability; if patches are unavailable for legacy systems, disable IP source routing at the network perimeter or via registry settings to block potentially malicious source-routed packets.

Fix this in Terminal Server Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA4.0 h
22.0 hours of engineering $3,860
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-1999-0909 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data