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Windows 2000Operating system · Microsoft

CVE-2009-2510

MEDIUM · 6.8 CVSS v2.0 Published 2009-10-14
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
77/100
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
The CryptoAPI component in Microsoft Windows 2000 SP4, Windows XP SP2 and SP3, Windows Server 2003 SP2, Windows Vista Gold, SP1, and SP2, Windows Server 2008 Gold, SP2, and R2, and Windows 7, as used by Internet Explorer and other applications, does not properly handle a '\0' character in a domain name in the subject's Common Name (CN) field of an X.509 certificate, which allows man-in-the-middle attackers to spoof arbitrary SSL servers via a crafted certificate issued by a legitimate Certification Authority, aka "Null Truncation in X.509 Common Name Vulnerability," a related issue to CVE-2009-2408.

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 confidence

The CryptoAPI in multiple Windows versions fails to properly handle null characters ('\0') in the Common Name (CN) field of X.509 certificates. When parsing certificate subject names, CryptoAPI stops at the null character, allowing attackers to craft certificates that appear valid for legitimate domains by appending a domain they control after a null byte in the CN field.

MitigationDeploy the relevant Microsoft security update (MS09-056) to patch the CryptoAPI component across all affected Windows systems, and verify that applications using CryptoAPI for certificate validation now correctly reject certificates with embedded null characters in the CN field.

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
Windows 2000Operating system
Affected:all versions
Windows 2003 ServerOperating system
Affected:all versions
Windows 7Operating system
Affected:all versions
Windows Server 2008Operating system
Affected:all versions
Windows VistaOperating system
Affected:all versions
Windows XpOperating system
Affected:all versions

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
M
Authentication
None
Confidentiality
Partial
Integrity
Partial
Availability
Partial

AV:N/AC:M/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 runs Windows 2000, Windows XP, Windows Server 2003, Windows Vista, Windows Server 2008, or Windows 7 (any version).
  2. Check if MS09-056 update is installed
    Open Control Panel > Programs and Features > View installed updates, or run 'wmic qfe list' command to list installed hotfixes. Search for update KB974571 (the MS09-056 patch).
    Affected if The MS09-056 security update (KB974571) is NOT installed on the system.
  3. Verify CryptoAPI component version
    Locate crypt32.dll in the system32 folder, right-click > Properties > Details to view the file version. Alternatively, run 'dir /a crypt32.dll' and check the version through PowerShell: (Get-Item C:\Windows\System32\crypt32.dll).VersionInfo.
    Affected if The crypt32.dll version is earlier than the patched version for MS09-056 (typically below 5.131.3790.4455 for XP/2003, or below 6.0.6001.1826 for Vista/2008).
  4. Test certificate validation behavior (if you manage PKI or certificates)
    Obtain or generate a test X.509 certificate with a null character ('\0') embedded in the Common Name field (e.g., 'legitimate-domain.com\0.attacker.com'). Attempt to validate this certificate using an application that relies on CryptoAPI for chain validation.
    Affected if The application accepts and validates the certificate as trusted for 'legitimate-domain.com', indicating the null byte is not being properly rejected.

A system is affected if it runs any version of Windows 2000, XP, 2003, Vista, Server 2008, or Windows 7 AND does not have the MS09-056 (KB974571) security update installed, allowing certificates with null bytes in the CN field to be incorrectly validated as trusted.

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

Deploy the relevant Microsoft security update (MS09-056) to patch the CryptoAPI component across all affected Windows systems, and verify that applications using CryptoAPI for certificate validation now correctly reject certificates with embedded null characters in the CN field.

Fix this in Windows 2000 Scoped from the published advisory
  • Consultation3.0 h
  • Implementation6.0 h
  • Testing4.0 h
  • Review / QA2.0 h
15.0 hours of engineering $2,640
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Scan for this in your stack

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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-2009-2510 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
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  • No spam, self-promotion, credentials, or personal data