How to Fix CVE-2009-1537: NULL Byte Overwrite in DirectX

By Sai Kiran Pandrala

Patch immediately. CISA added CVE-2009-1537 to the Known Exploited Vulnerabilities catalog on 2026-05-20. Federal civilian agencies must remediate by 2026-06-03. Treat every internet-reachable instance as a priority patch.

What is CVE-2009-1537?

CVE-2009-1537 is a NULL Byte Overwrite flaw in Microsoft DirectX. It carries a CVSS base score of 8.8 (high). CISA confirmed real-world exploitation by adding it to the Known Exploited Vulnerabilities catalog on 2026-05-20.

From the source record: Unspecified vulnerability in the QuickTime Movie Parser Filter in quartz.dll in DirectShow in Microsoft DirectX 7.0 through 9.0c on Windows 2000 SP4, Windows XP SP2 and SP3, and Windows Server 2003 SP2 allows remote attackers to execute arbitrary code via a crafted QuickTime media file, as exploited in the wild in May 2009, aka "DirectX NULL Byte Overwrite Vulnerability."

Why it matters in practice: KEV-listed CVEs draw continuous internet-wide scanning. Any unpatched, internet-reachable installation is on borrowed time. The blast radius depends on how the affected service is exposed. An internet-facing instance with no compensating controls is the highest-risk configuration.

Am I affected?

You are affected if your installation of DirectX matches a version listed in the Affected row above.

On Windows, check the installed version with PowerShell:

# Generic - list installed product versions
Get-CimInstance Win32_Product | Where-Object Name -like "*DirectX*" | Select-Object Name, Version
# Windows updates installed (KB lookup)
Get-HotFix | Sort-Object InstalledOn -Descending | Select-Object -First 20

How to fix CVE-2009-1537

Apply the vendor patch. Target the patched build listed on the vendor advisory. The runnable command set below covers the most common deployment patterns for DirectX.

Windows (PowerShell, run as administrator)

# 1) Backup affected service config
$stamp = Get-Date -Format yyyyMMdd-HHmm
$backup = "C:\Backup\directx-$stamp"
New-Item -ItemType Directory -Path $backup -Force | Out-Null

# 2) Install the latest Windows security updates (the patch for CVE-2009-1537 ships here)
Install-Module PSWindowsUpdate -Force -Scope CurrentUser -ErrorAction SilentlyContinue
Import-Module PSWindowsUpdate
Get-WindowsUpdate -MicrosoftUpdate -AcceptAll -Install -AutoReboot

# 3) Confirm the patch landed
Get-HotFix | Sort-Object InstalledOn -Descending | Select-Object -First 10

Vendor-managed app on Windows (winget)

# Vendor advisory: https://learn.microsoft.com/en-us/security-updates/securitybulletins/2009/ms09-028
winget upgrade --all --silent --accept-package-agreements --accept-source-agreements
# or target the specific package:
winget search "DirectX"
winget upgrade --id <PackageId> --silent

Complete PowerShell patch script

# Patch DirectX for CVE-2009-1537
$log = "C:\Backup\CVE-2009-1537-patch.log"
"[{0}] Starting patch run" -f (Get-Date) | Tee-Object -FilePath $log -Append
try {
    $stamp = Get-Date -Format yyyyMMdd-HHmm
    $backup = "C:\Backup\directx-$stamp"
    New-Item -ItemType Directory -Path $backup -Force | Out-Null
    # Backup hook - tailor for the product
    # Copy-Item "C:\Program Files\DirectX" $backup -Recurse -ErrorAction SilentlyContinue

    if (-not (Get-Module -ListAvailable PSWindowsUpdate)) {
        Install-Module PSWindowsUpdate -Force -Scope CurrentUser
    }
    Import-Module PSWindowsUpdate
    Get-WindowsUpdate -MicrosoftUpdate -AcceptAll -Install -AutoReboot:$false -IgnoreReboot
    "[{0}] Updates installed" -f (Get-Date) | Tee-Object -FilePath $log -Append
    # Verify
    Get-HotFix | Sort-Object InstalledOn -Descending | Select-Object -First 5 | Out-File $log -Append
    "[{0}] Patch run complete - reboot at next maintenance window" -f (Get-Date) | Tee-Object -FilePath $log -Append
} catch {
    "[{0}] ERROR: $_" -f (Get-Date) | Tee-Object -FilePath $log -Append
    exit 1
}

After applying the patch

1. Restart the service or device so the patched binary loads.
2. Confirm the running version matches the Fixed in row using the verification command below.
3. Rotate credentials and API keys that the affected service could access if the asset was exposed during the disclosure window.

If you can't patch immediately

Until the patch lands, narrow the attack surface with these runnable controls.

Restrict the affected service via Windows Firewall

# Replace -RemoteAddress with your trusted admin range
New-NetFirewallRule -DisplayName "Block CVE-2009-1537 inbound" -Direction Inbound -Action Block -Protocol TCP -LocalPort 445,3389,5985
New-NetFirewallRule -DisplayName "Allow CVE-2009-1537 admin range" -Direction Inbound -Action Allow -Protocol TCP -LocalPort 445,3389,5985 -RemoteAddress 10.10.10.0/24

Disable the vulnerable feature if the vendor advisory allows it

# Vendor advisory: https://learn.microsoft.com/en-us/security-updates/securitybulletins/2009/ms09-028
# Example: stopping a non-essential Windows service
Stop-Service -Name <ServiceName> -Force
Set-Service -Name <ServiceName> -StartupType Disabled

Mitigations are temporary. Apply the vendor patch as soon as a maintenance window opens.

How to verify the fix worked

Confirm the patched build is the one actually running.

# Confirm KB / hotfix is present
Get-HotFix | Sort-Object InstalledOn -Descending | Select-Object -First 10
# Confirm product version
Get-CimInstance Win32_Product | Where-Object Name -like "*DirectX*" | Select-Object Name, Version

Expected: the patched build named in Fixed in (See vendor advisory) appears in the version column.

Also worth doing: pull recent log windows for any indicators of compromise listed in the vendor advisory, and re-run an authenticated vulnerability scan with up-to-date signatures.

Frequently asked questions

Related fixes

Other vulnerabilities in the same area that are worth patching alongside this one:

• How to Fix CVE-2009-0563: Out-of-bounds Write in Office — Out-of-bounds Write in Office
• How to Fix CVE-2009-0557: Improper Control of Generation of Code ('Code Injection') in Office — Improper Control of Generation of Code ('Code Injection') in Office
• How to Fix CVE-2009-0556: Memory Corruption in Office , Memory Corruption in Office
• How to Fix CVE-2009-1123: Security vulnerability in Microsoft Windows , Security vulnerability in Microsoft Windows
• How to Fix CVE-2009-3129: Out-of-bounds write in Microsoft Office , Out-of-bounds write in Microsoft Office

Is CVE-2009-1537 being exploited in the wild?

Yes. CISA added CVE-2009-1537 to the Known Exploited Vulnerabilities catalog on 2026-05-20. KEV listing means at least one confirmed real-world exploitation report exists.

Do I have to take downtime to patch?

For most Microsoft DirectX deployments, the patched build needs a service restart or device reboot. HA pairs and clusters can roll the upgrade by patching the standby first, failing over, then patching the former primary.

Will a WAF or IDS rule alone close CVE-2009-1537?

No. Network filters cut down opportunistic scans but they do not remove the flaw. The vendor patch is the only durable fix.

How quickly should I act on CVE-2009-1537?

Within the standard patch cycle if the asset is internal-only. Inside one to two weeks for any internet-facing instance, sooner if compensating controls are not in place.

References

• Official vendor advisory: https://learn.microsoft.com/en-us/security-updates/securitybulletins/2009/ms09-028
• NVD entry: https://nvd.nist.gov/vuln/detail/CVE-2009-1537
• CISA KEV catalog: https://www.cisa.gov/known-exploited-vulnerabilities-catalog
• CISA KEV entry: "Microsoft DirectX NULL Byte Overwrite Vulnerability" - added 2026-05-20, due 2026-06-03
• Additional reference: http://blogs.technet.com/msrc/archive/2009/05/28/microsoft-security-advisory-971778-vulnerability-in-microsoft-directshow-released.aspx
• Additional reference: http://blogs.technet.com/srd/archive/2009/05/28/new-vulnerability-in-quicktime-parsing.aspx
• Additional reference: http://isc.sans.org/diary.html?storyid=6481
• Additional reference: http://osvdb.org/54797

*Assembled from the official vendor advisory, the NVD record, and the CISA KEV listing on 2026-05-25. Always confirm against the vendor advisory before applying changes in production.*