CVE-2009-3129
HIGHCVE-2009-3129 is a high-severity (CVSS 7.8) Out-of-bounds Write vulnerability in microsoft excel. It is in CISA's Known Exploited Vulnerabilities catalog (added 2022-03-03) — treat it as actively exploited and patch now. O3 Security detects and blocks CVE-2009-3129 exploitation at runtime via eBPF exploit-chain detection and L7 egress monitoring, even on unpatched systems.
Microsoft Office Excel 2002 SP3, 2003 SP3, and 2007 SP1 and SP2; Office 2004 and 2008 for Mac; Open XML File Format Converter for Mac; Office Excel Viewer 2003 SP3; Office Excel Viewer…
Exploitation Status
Actively exploited in the wild
- Confirmed by CISA's Known Exploited Vulnerabilities catalog on 2022-03-03. Federal agencies were required to remediate by 2022-03-24.
- A successful exploit gives an attacker total control of the affected component, not partial access.
Exploitation and automatability from CISA (KEV catalog and SSVC triage) for CVE-2009-3129.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2009-3129 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE sits: patch-first territory.
Where this sits among everything scored
Of 368,770 CVEs with a current EPSS score, this one falls in the 50–90% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Description
Microsoft Office Excel 2002 SP3, 2003 SP3, and 2007 SP1 and SP2; Office 2004 and 2008 for Mac; Open XML File Format Converter for Mac; Office Excel Viewer 2003 SP3; Office Excel Viewer SP1 and SP2; and Office Compatibility Pack for Word, Excel, and PowerPoint 2007 File Formats SP1 and SP2 allows remote attackers to execute arbitrary code via a spreadsheet with a FEATHEADER record containing an invalid cbHdrData size element that affects a pointer offset, aka "Excel Featheader Record Memory Corruption Vulnerability."
Affected Products
excelmicrosoftexcel viewermicrosoftofficemicrosoftopen xml file format convertermicrosoftResearch use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Microsoft Excel - Malformed FEATHEADER Record (MS09-067) (Metasploit)
by Metasploit · Sep 25, 2010
Microsoft Excel - FEATHEADER Record (MS09-067)
by anonymous · Aug 21, 2010
Detection & mitigation playbook
Vendor / applianceDetect
Inventory every microsoft excel deployment and check each version against the affected-products list above. Because the exploit targets the running system rather than your application code, also watch for remote code execution at the network and runtime layer — O3 flags the exploit behaviour from runtime telemetry and egress traffic even before a vulnerable build is confirmed.
Remediation status
No patch has shipped for CVE-2009-3129 yet — track the microsoft excel advisory for a fixed release and apply the workarounds below in the meantime.
Mitigate without a patch
Cut exposure now: restrict the management/admin interface to trusted networks, segment the device, and apply the vendor's recommended configuration mitigations and any WAF/IPS signature. O3's runtime protection blocks the exploit chain at execution, holding the line on unpatched or end-of-life systems until you can patch.
How O3 protects you
O3 detects and blocks CVE-2009-3129 exploitation at runtime: eBPF exploit-chain detection, plus L7 egress monitoring that catches the post-exploitation callback and severs the attacker's outbound channel.
Tailored to CVE-2009-3129. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2009-3129 being exploited in your environment?
O3's eBPF runtime sensors and L7 egress monitoring detect and block the CVE-2009-3129 exploit chain at execution — protecting unpatched and end-of-life systems until the vendor patch is applied.