CriticalCVE-2009-1537

    Microsoft DirectX NULL Byte Overwrite Vulnerability (CVE-2009-1537)

    Published In CISA KEV since Sources: CVE.org

    What is affected, what to do

    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."

    The vulnerability is being actively exploited; treat it as a priority. The available sources name no fixed version. Check the vendor guidance in the references below. Immediate actions, mitigation and detection rules are in the runbook below.

    Affected
    • Microsoft DirectX eq 7.0..7.0
    • Microsoft DirectX eq 7.0a..7.0a
    • Microsoft DirectX eq 7.1..7.1
    • Microsoft DirectX eq 8.1..8.1
    • Microsoft DirectX eq 8.1b..8.1b
    • Microsoft DirectX eq 9.0..9.0
    • Microsoft DirectX eq 9.0a..9.0a
    • Microsoft DirectX eq 9.0b..9.0b
    • Microsoft DirectX eq 9.0c..9.0c

    Not sure whether and how you are affected? Ask a question about this vulnerability

    Metrics

    8.8

    Priority

    XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.

    Source: NVD, CVSS v3

    8.8

    CVSS v3

    Severity High on the scale from 0 to 10.

    Source: CVE.org

    51.4 %

    EPSS score

    High — model estimates ≥ 50% chance of real-world exploitation within 30 days.

    Source: FIRST EPSS, percentile 98.9

    Show all metrics
    Severity
    Critical
    Priority (0–325)

    The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?

    Read in glossary
    222.30 Methodology
    Exploit maturity

    An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.

    Read in glossary
    actively exploited
    XIEM Effective CVSS

    XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.

    Read in glossary
    8.8 Methodology
    CVSS v3

    CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.

    Read in glossary
    8.8
    EPSS score

    The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.

    Read in glossary
    51.4 %
    High — model estimates ≥ 50% chance of real-world exploitation within 30 days.
    EPSS percentile

    The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.

    Read in glossary
    98.9
    Critical — this CVE ranks in the top fifth of all CVEs scored today (rank ≥ 80%).
    KEV status

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    Actively exploited
    Published
    In CISA KEV since

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    CISA assessment (SSVC)
    Exploitation: active · not automatable · Technical impact: total
    Source: CISA Vulnrichment, as of 20 May 2026
    CWE

    CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.

    Read in glossary
    CWE-158

    Response and mitigation

    Why act now?

    Prioritisation rationale

    This flaw is network-reachable without authentication and needs only a user to open a crafted media file or visit a malicious page. Successful exploitation yields full code execution with high impact on confidentiality, integrity and availability. Exploitation likelihood remains very high despite the bug's age, because public exploits have been embedded in common frameworks for years; CISA does not flag ransomware use. If your estate contains no Windows 2000/XP/2003, the risk is negligible. Where such hosts persist, typically in OT, medical or lab environments, treat this as critical: these systems are usually unpatched and poorly monitored, which makes them ideal footholds into sensitive network zones.

    1. Runbook step 1

      Immediate response (0-24 h)

      • Inventory legacy hosts: Enumerate every Windows 2000 SP4, Windows XP SP2/SP3 and Windows Server 2003 SP2 system via CMDB, the AD operatingSystem attribute and network scans. Expect to find them in HMI/SCADA workstations, medical and lab devices, kiosks, POS terminals and embedded controllers.
      • Patch where still possible: Microsoft released a fix for DirectShow/quartz.dll (to our knowledge bulletin MS09-028, KB971633 — verify in the vendor advisory). All affected OS versions have long been end-of-life. Treat any unpatched host as permanently exposed and apply compensating controls.
      • Disable the QuickTime parser (workaround): If patching is blocked, unregister the QuickTime Movie Parser Filter. Microsoft's workaround removes HKCR\CLSID\{D51BD5A0-7548-11CF-A520-0080C77EF58A}; verify the CLSID against the vendor advisory. Back up the key with reg export first, then confirm the business application still works.
      • Restrict network access now: Block web browsing, email clients and ad-hoc file exchange on affected hosts. These are the delivery paths for crafted media: drive-by pages, attachments and file shares.
      • Block media playback: Remove file associations for .mov, .qt and .moov on legacy systems. Disable the Windows Media Player/DirectShow ActiveX plug-in in Internet Explorer via kill-bit or GPO.

    2. Runbook step 2

      Mitigation layers

      • Network segmentation: Move EOL systems into a dedicated default-deny segment or VLAN. Deny outbound HTTP/HTTPS (TCP 80/443) and SMB (TCP 445) to the internet. Allow only explicitly required flows to process or application servers (IEC 62443 zone/conduit model).
      • Proxy/secure web gateway: Block video/quicktime MIME types and the .mov/.qt extensions for clients in the legacy segment. Force sandbox detonation for all other clients.
      • Email gateway: Quarantine QuickTime containers in attachments and archives. Confirm whether the business needs this file type at all; if not, block it permanently.
      • IPS/IDS: Enable Suricata/Snort signatures for malformed QuickTime atoms and DirectShow exploits (ET EXPLOIT/WEB_CLIENT categories, search for "QuickTime" or "DirectShow"). Run them in blocking mode on conduits into the legacy segment.
      • Endpoint hardening and least privilege: Ensure legacy users do not run with admin rights, which limits the impact of user-context code execution. Enforce application allow-listing (Software Restriction Policies on XP/2003) and set DEP to OptOut/AlwaysOn where supported.
      • Strategic: Record a formal risk acceptance and migration plan for every remaining EOL host. This aligns with NIS2 Art. 21 and BSI IT-Grundschutz SYS.2.1.

    3. Runbook step 3

      Detection rules

      • Network telemetry (Zeek): Query files.log for mime_type == "video/quicktime" where the receiving host is in the EOL range. This is the primary source, since XP/2003 often lacks modern endpoint telemetry. Example: index=zeek sourcetype=zeek_files mime_type="video/quicktime" rx_hosts IN (<EOL-range>)
      • Process ancestry (EDR/Sysmon EID 1 where supported): Flag child processes spawned by media or browser processes. Sigma shape: ParentImage|endswith: ['\wmplayer.exe','\iexplore.exe','\mplayer2.exe'] AND Image|endswith: ['\cmd.exe','\powershell.exe','\wscript.exe','\rundll32.exe']
      • Image load (Sysmon EID 7): Alert when quartz.dll loads into a browser or Office process and is quickly followed by an outbound connection to a rare external IP (EID 3) or by .exe/.dll creation under %TEMP% (EID 11).
      • Crash artefacts: Look for Application log Event ID 1000/1001 (Application Error/Dr. Watson) naming quartz.dll as the faulting module in wmplayer.exe or iexplore.exe. These crashes can indicate failed exploitation attempts.
      • Proxy logs: Flag a *.mov/*.qt fetch followed within 60 seconds by an executable download from the same client. KQL shape: CommonSecurityLog | where RequestURL matches regex @"\.(mov|qt)(\?|$)"

    Detection rules

    No NEOSEC detection rule is available for this vulnerability yet.

    Classification under NIS2 and CRA

    Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

    NIS2

    NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.

    Read in glossary
    Actively exploited: treat the vulnerability as a priority in vulnerability handling under Art. 21(2)(e) NIS2. If it is exploited in your environment, check the reporting obligation under Art. 23 (early warning within 24 hours).
    CRA

    The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.

    Read in glossary
    Since 11.09.2026, manufacturers of affected products with digital elements must report actively exploited vulnerabilities under Art. 14 CRA, with an early warning within 24 hours via ENISA's single reporting platform.
    ISO/IEC 27001

    ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.

    Read in glossary
    Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

    Description

    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."

    Source: NVD (NIST), cvelistv5, CISA KEV Catalog

    Affected products

    The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

    Affected products
    Affected versionsFixed in
    microsoftdirectx
    • 7.0a
    • 7.1
    • 9.0
    • 9.0c
    • 8.1
    • 8.1b
    • 9.0a
    • 9.0b
    • 7.0
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —

    Vendors and products

    Affected operating systems

    Affected operating systems
    Windowsmicrosoftwindows_2000—
    Windowsmicrosoftwindows_2003_server—
    Windowsmicrosoftwindows_server_2003—
    Windowsmicrosoftwindows_xp—

    Weakness classes (CWE)

    • CWE-158Improper Neutralization of Null Byte or NUL Character

      Variant

      The product receives input from an upstream component, but it does not neutralize or incorrectly neutralizes NUL characters or null bytes when they are sent to a downstream component.

      Entry at MITRE CWE-158

    Public exploit references

    Publicly reported proof-of-concepts, exploit modules and detection templates for this vulnerability. NEOSEC links to the original sources only and does not provide any exploit code.

    Public exploit references
    CISA KEV CatalogCISA Known Exploited Vulnerability (opens in a new tab)cisa.govactively exploited

    References & sources

    • docs.microsoft.comMS09-028Vendor advisory, x_refsource_MS, Vendor advisory
    • blogs.technet.comsrd/archive/2009/05/28/new-vulnerability-in-quicktime-parsing.a…x_refsource_CONFIRM, Vendor advisory
    • oval.cisecurity.orgoval:org.mitre.oval:def:6237Vulnerability database, signature, x_refsource_OVAL, Broken link
    • secunia.com35268Third-party advisory, x_refsource_SECUNIA, Vendor advisory
    • securitytracker.com1022299Vulnerability database, x_refsource_SECTRACK, Broken link
    • vupen.comADV-2009-1886Vulnerability database, x_refsource_VUPEN, Vendor advisory
    • vupen.comADV-2009-1445Vulnerability database, x_refsource_VUPEN, Vendor advisory
    • osvdb.org54797Vulnerability database, x_refsource_OSVDB, Broken link
    • securityfocus.com35139Vulnerability database, x_refsource_BID, Broken link
    • us-cert.govTA09-195AThird-party advisory, x_refsource_CERT, US government resource
    • isc.sans.orgdiary.html?storyid=6481x_refsource_MISC, Not applicable
    • microsoft.comtechnet/security/advisory/971778.mspxx_refsource_CONFIRM, Patch, Vendor advisory
    • blogs.technet.commsrc/archive/2009/05/28/microsoft-security-advisory-971778-vuln…x_refsource_CONFIRM, Vendor advisory
    • cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2009-1537government-resource, US government resource
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