CVE-2001-0546
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 · uneditedMemory leak in H.323 Gatekeeper Service in Microsoft Internet Security and Acceleration (ISA) Server 2000 allows remote attackers to cause a denial of service (resource exhaustion) via a large amount of malformed H.323 data.
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 · high confidenceThe H.323 Gatekeeper Service in Microsoft ISA Server 2000 contains a memory leak that is triggered when remote attackers send large quantities of malformed H.323 protocol data. This causes progressive memory exhaustion, eventually leading to service failure and denial of service.
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= 2000CVSS 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
- None
- Integrity
- None
- Availability
- Partial
AV:N/AC:L/Au:N/C:N/I:N/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 checksWork through these to decide whether this CVE applies to you.
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Confirm ISA Server 2000 installationCheck the installed programs or the version of ISA Server by examining the program files directory, registry key HKLM\SOFTWARE\Microsoft\ISA Server, or the ISA Server Management console informationAffected if The installed version is Microsoft ISA Server 2000
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Verify H.323 Gatekeeper Service is enabledOpen Services console (services.msc) and locate 'H.323 Gatekeeper Service' or check the ISA Server Management console under Extensions > Application FiltersAffected if The H.323 Gatekeeper Service is installed and enabled in ISA Server 2000
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Check if H.323 protocol filtering is activeExamine ISA Server policy rules or filtering configuration for any rules that allow or handle H.323 protocol traffic (port 1720 typically)Affected if H.323 protocol filtering or gatekeeper functionality is actively configured in ISA Server 2000
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Monitor service memory consumptionUse Task Manager or Performance Monitor to observe the memory usage of the ISA Server services over time, particularly if experiencing slownessAffected if The ISA Server services show abnormally high and progressively increasing memory usage
A system is affected if it runs Microsoft ISA Server 2000 with the H.323 Gatekeeper Service enabled and processing H.323 traffic, which can lead to memory exhaustion from malformed packets.
Generated from the published advisory. Verify against your own configuration.
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 dataApply any available Microsoft security patches for ISA Server 2000, or if no patch is available, disable the H.323 Gatekeeper Service if not required, or implement network-level filtering to restrict H.323 traffic to trusted sources.
- Consultation2.0 h
- Implementation4.0 h
- Testing2.0 h
- Review / QA1.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2001-0546 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2001-0546 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- 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
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