Microsoft Windows Improper Input Validation Vulnerability (CVE-2009-1123)
Published In CISA KEV since Sources: CVE.org
What is affected, what to do
The kernel in Microsoft Windows 2000 SP4, XP SP2 and SP3, Server 2003 SP2, Vista Gold, SP1, and SP2, and Server 2008 SP2 does not properly validate changes to unspecified kernel objects, which allows local users to gain privileges via a crafted application, aka "Windows Kernel Desktop 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.
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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
4.9 %
EPSS score
Moderate — model estimates 1-10% exploitation likelihood.
Source: FIRST EPSS, percentile 92.0
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- 206.77 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- 4.9 %
- Moderate — model estimates 1-10% exploitation likelihood.
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- 92.0
- 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 4 February 2025
Response and mitigation
Why act now?
Prioritisation rationale
This is a local kernel privilege escalation. An attacker needs no prior privileges but must get a crafted application executed, so it is used as a second-stage step after phishing or drive-by initial access to move from user to SYSTEM. Exploitation likelihood is elevated relative to most CVEs, and CISA does not flag known ransomware use. For estates with current patching and no legacy Windows, residual risk is low. Where XP, 2003 or 2008 systems still run, for example in OT or KRITIS operations, rate it high: these platforms lack modern exploit mitigations, and compromise there often goes unnoticed.
Runbook step 1
Immediate response (0-24 h)
- Inventory legacy hosts: Identify every Windows 2000 SP4, XP SP2/SP3, Server 2003 SP2, Vista (Gold/SP1/SP2) and Server 2008 SP2 system via CMDB, AD query (
Get-ADComputer -Filter * -Properties OperatingSystem) or network scan. Include OT/HMI, medical and lab workstations, which is where these platforms typically survive. - Verify the patch: Microsoft fixed this issue (the "Windows Kernel Desktop Vulnerability") with a 2009 security update, to our knowledge bulletin MS09-025. Confirm the bulletin and KB number in the vendor advisory and prove installation with
wmic qfe listor your inventory tool. Deploy immediately where missing. - Account for end of life: Every affected version is out of support. Treat any host without proven patch status as non-hardenable. Trigger migration, or obtain a documented risk acceptance from the asset owner as part of NIS2 risk management.
- Restrict local logon: Limit interactive and RDP logon on legacy hosts to named administrators. Review shared kiosk and operator accounts.
- Compromise check: On hosts that were unpatched and used by end users, review local administrator membership, services and autorun entries for unexpected changes.
- Inventory legacy hosts: Identify every Windows 2000 SP4, XP SP2/SP3, Server 2003 SP2, Vista (Gold/SP1/SP2) and Server 2008 SP2 system via CMDB, AD query (
Runbook step 2
Mitigation layers
- Network segmentation: Move legacy hosts into a dedicated VLAN/zone (IEC 62443 zones and conduits). Block SMB (445/tcp) and RDP (3389/tcp) from the corporate network and deny outbound internet access. This makes it harder to deliver the crafted application the attack depends on.
- Application control: Enforce Software Restriction Policies in allowlist mode on XP/2003, and SRP or a third-party allowlisting product on Vista/2008. Deny execution from
%TEMP%,%APPDATA%, Downloads and removable media. - Removable media and file transfer: Block USB mass storage via GPO. Route file imports through a scanning kiosk or data diode workflow.
- Least privilege: Run end users without local admin rights. Set unique local administrator passwords per host so a successful escalation cannot be replayed laterally.
- Endpoint protection: Deploy an EDR/AV agent that still supports legacy OS builds where available. Otherwise, place network monitoring (Zeek/Suricata) at the segment boundary as a compensating control.
Runbook step 3
Detection rules
- Process creation with privilege jump: Enable process tracking via audit policy, then watch Event 4688 (Vista/2008) or 592 (XP/2003). Flag
cmd.exeorpowershell.exerunning asNT AUTHORITY\SYSTEMwhose parent lives in a user-writable path. Sigma shape:ParentImage|contains: '\Users\' OR '\Documents and Settings\'ANDSubjectUserName: SYSTEM. - New privileged accounts: Watch Events 4720/4732 (Vista/2008) or 624/636 (XP/2003), meaning new accounts or additions to "Administrators" outside change windows. SPL:
index=wineventlog (EventCode=4732 OR EventCode=636) Group_Name="Administrators". - Service installation: Monitor System log Event 7045 or 7035/7036 for binaries located in Temp or user profile paths. This is a common persistence step after kernel-level escalation.
- Unsigned binaries on legacy hosts: Track first-seen executables via SRP events (865–868) or AV telemetry.
- Network: Treat Zeek
smb_files.log/http.logentries showing PE files transferred into the legacy segment, and new outbound connections from legacy hosts, as signs of a staging step.
- Process creation with privilege jump: Enable process tracking via audit policy, then watch Event 4688 (Vista/2008) or 592 (XP/2003). Flag
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
The kernel in Microsoft Windows 2000 SP4, XP SP2 and SP3, Server 2003 SP2, Vista Gold, SP1, and SP2, and Server 2008 SP2 does not properly validate changes to unspecified kernel objects, which allows local users to gain privileges via a crafted application, aka "Windows Kernel Desktop Vulnerability."
Source: NVD (NIST), cvelistv5, CISA KEV Catalog, CVE.org (MITRE)
Vendors and products
Affected operating systems
| Windows | microsoft | windows_2000 | — |
| Windows | microsoft | windows_server_2003 | — |
| Windows | microsoft | windows_server_2008 | — |
| Windows | microsoft | windows_vista | — |
| Windows | microsoft | windows_xp | — |
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.
| CISA KEV Catalog | CISA Known Exploited Vulnerability (opens in a new tab)cisa.gov | actively exploited |
References & sources
- secunia.com35372Third-party advisory, x_refsource_SECUNIA, Broken link
- osvdb.org54940Vulnerability database, x_refsource_OSVDB, Broken link
- vupen.comADV-2009-1544Vulnerability database, x_refsource_VUPEN, Broken link
- docs.microsoft.comMS09-025Vendor advisory, x_refsource_MS, Patch, Vendor advisory
- securitytracker.com1022359Vulnerability database, x_refsource_SECTRACK, Broken link, Third-party advisory, Vulnerability database
- oval.cisecurity.orgoval:org.mitre.oval:def:6206Vulnerability database, signature, x_refsource_OVAL, Broken link
- us-cert.govTA09-160AThird-party advisory, x_refsource_CERT, Broken link, Third-party advisory, US government resource
- cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2009-1123government-resource, US government resource
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