CriticalCVE-2009-0563

    Microsoft Office Buffer Overflow Vulnerability (CVE-2009-0563)

    Published In CISA KEV since Sources: CVE.org

    What is affected, what to do

    Stack-based buffer overflow in Microsoft Office Word 2002 SP3, 2003 SP3, and 2007 SP1 and SP2; Microsoft Office for Mac 2004 and 2008; Open XML File Format Converter for Mac; Microsoft Office Word Viewer 2003 SP3; Microsoft Office Word Viewer; and Microsoft Office Compatibility Pack for Word, Excel, and PowerPoint 2007 File Formats SP1 and SP2 allows remote attackers to execute arbitrary code via a Word document with a crafted tag containing an invalid length field, aka "Word Buffer Overflow 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 Office eq 2000..2000
    • Microsoft Office eq 2003..2003
    • Microsoft Office eq 2004..2004
    • Microsoft Office eq 2007..2007
    • Microsoft Office eq 2008..2008
    • Microsoft Office eq xp..xp
    • Microsoft Office Compatibility Pack Service Pack 3 eq 2007..2007
    • Microsoft Office Word Viewer eq 2003..2003

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

    Metrics

    7.8

    Priority

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

    Source: NVD, CVSS v3

    7.8

    CVSS v3

    Severity High on the scale from 0 to 10.

    Source: CVE.org

    59.6 %

    EPSS score

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

    Source: FIRST EPSS, percentile 99.12

    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
    217.60 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
    7.8 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
    7.8
    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
    59.6 %
    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
    99.12
    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 10 February 2025
    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-787

    Response and mitigation

    Why act now?

    Prioritisation rationale

    This is a classic stack overflow in the Word parser: simply opening a crafted document — no macros, no privileges — yields code execution in the user's context, which made it a staple of targeted spear-phishing and keeps it among the Office CVEs most likely to be exploited despite requiring user interaction. CISA does not flag known ransomware use. For organisations with no Office builds older than 2010 the practical risk is low and inventory confirmation is the key action; where legacy Office persists on OT, archive or line-of-business systems, treat it as high priority, because those hosts receive no further updates and represent a permanent, easily weaponised entry point.

    1. Runbook step 1

      Immediate response (0-24 h)

      • Run an inventory sweep: Identify every endpoint and terminal server running Word 2002 (XP) SP3, Word 2003 SP3, Word 2007 SP1/SP2, Word Viewer 2003 / Word Viewer, Office Compatibility Pack 2007, Office for Mac 2004/2008, or the Open XML File Format Converter for Mac. Look for wwlib.dll / WINWORD.EXE major version 10.x, 11.x or 12.x and wordview.exe via EDR, SCCM/Intune software inventory, or Get-ItemProperty HKLM:\SOFTWARE\WOW6432Node\Microsoft\Office\*.
      • Patch or remove: A vendor patch is available — look up the exact version in the vendor advisory. All affected products have been end-of-life for years, so the real fix is uninstalling them and migrating to a supported Office build (Microsoft 365 Apps / Office LTSC).
      • Isolate hosts that cannot be migrated: Move systems that genuinely depend on legacy Office (OT engineering workstations, archive or line-of-business clients) into a dedicated segment with no email or internet access.
      • Tighten the mail gateway: Quarantine or sandbox-detonate inbound binary Word files (.doc, .dot, .rtf with embedded Word objects) from external senders; allow exceptions only through a release workflow.
      • Hunt for compromise: On hosts with a vulnerable version, run the detection queries below retroactively (at least 90 days). On a hit, isolate the host, capture memory and reset the affected user's credentials.

    2. Runbook step 2

      Mitigation layers

      • Network segmentation: Place legacy-Office hosts in a VLAN with outbound traffic restricted to defined internal services; block outbound HTTP/HTTPS and SMB (445/TCP) to the internet to stop second-stage payload retrieval.
      • Endpoint hardening (Microsoft Defender ASR): Enable in block mode "Block all Office applications from creating child processes" (D4F940AB-401B-4EFC-AADC-AD5F3C50688A), "Block Office applications from creating executable content" and "Block Office applications from injecting code into other processes". Enforce DEP/ASLR system-wide via Exploit Protection (Set-ProcessMitigation).
      • Configuration change: Use Office Group Policy File Block settings to block Word 97-2003 binary formats or force them into Protected View; block Word Viewer and the Compatibility Pack as unapproved software via AppLocker/WDAC.
      • IAM / least privilege: Run legacy-Office users without local admin rights; code executes in the user context, so removing admin rights limits persistence and lateral movement.
      • Gateway / sandbox: Detonate email and web-sourced documents before delivery; keep vendor AV/YARA signatures for malformed length fields in Word binary structures (CVE-2009-0563 coverage) enabled.

    3. Runbook step 3

      Detection rules

      • Sysmon EID 1 / EDR process ancestry: ParentImage ends with \WINWORD.EXE or \wordview.exe and Image in (cmd.exe, powershell.exe, wscript.exe, cscript.exe, mshta.exe, rundll32.exe, regsvr32.exe). KQL: DeviceProcessEvents | where InitiatingProcessFileName in~ ("winword.exe","wordview.exe") and FileName in~ ("cmd.exe","powershell.exe","mshta.exe","rundll32.exe","regsvr32.exe","wscript.exe").
      • Windows Application log Event ID 1000/1001: WINWORD.EXE crashes with faulting module wwlib.dll or mso.dll, especially shortly after an email attachment is opened — a strong sign of failed exploitation attempts.
      • Sysmon EID 11: WINWORD.EXE writing .exe, .dll, .scr or .vbs files into %TEMP%, %APPDATA% or C:\ProgramData.
      • Sysmon EID 3 / Zeek conn.log: Outbound connections initiated directly by WINWORD.EXE to external IPs, particularly on non-standard ports.
      • Mail gateway logs: .doc attachments delivered to recipients whose endpoint is tagged as a legacy-Office host in the inventory — correlate in the SIEM as elevated risk.

    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

    Stack-based buffer overflow in Microsoft Office Word 2002 SP3, 2003 SP3, and 2007 SP1 and SP2; Microsoft Office for Mac 2004 and 2008; Open XML File Format Converter for Mac; Microsoft Office Word Viewer 2003 SP3; Microsoft Office Word Viewer; and Microsoft Office Compatibility Pack for Word, Excel, and PowerPoint 2007 File Formats SP1 and SP2 allows remote attackers to execute arbitrary code via a Word document with a crafted tag containing an invalid length field, aka "Word Buffer Overflow Vulnerability."

    Source: NVD (NIST), cvelistv5, CISA KEV Catalog, CVE.org (MITRE)

    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
    microsoftoffice
    • 2000
    • xp
    • 2003
    • 2007
    • 2008
    • 2004
    • —
    • —
    • —
    • —
    • —
    • —
    microsoftoffice_compatibility_pack
    • 2007
    • —
    microsoftoffice_word_viewer
    • 2003
    • —
    • —
    • —
    microsoftopen_xml_file_format_converter
    • —
    • —

    Vendors and products

    Weakness classes (CWE)

    • CWE-787Out-of-bounds Write

      Base

      The product writes data past the end, or before the beginning, of the intended buffer.

      Entry at MITRE CWE-787

    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

    • oval.cisecurity.orgoval:org.mitre.oval:def:6133Vulnerability database, signature, x_refsource_OVAL, Broken link
    • securityfocus.com35188Vulnerability database, x_refsource_BID, Broken link, Third-party advisory, Vulnerability database
    • osvdb.org54959Vulnerability database, x_refsource_OSVDB, Broken link
    • zerodayinitiative.comadvisories/ZDI-09-035x_refsource_MISC, Third-party advisory, Vulnerability database
    • us-cert.govTA09-160AThird-party advisory, x_refsource_CERT, Broken link, Third-party advisory, US government resource
    • securitytracker.com1022356Vulnerability database, x_refsource_SECTRACK, Broken link, Third-party advisory, Vulnerability database
    • docs.microsoft.comMS09-027Vendor advisory, x_refsource_MS, Patch, Vendor advisory
    • vupen.comADV-2009-1546Vulnerability database, x_refsource_VUPEN, Broken link
    • securityfocus.com20090610 ZDI-09-035: Microsoft Word Document Stack Based Buffer Overflow VulnerabilityMailing list, x_refsource_BUGTRAQ, Broken link, Third-party advisory, Vulnerability database
    • cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2009-0563government-resource, US government resource
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