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HighCISA KEVExploited in the wildPublic exploit

Excel FEATHEADER Record Memory Corruption Vulnerability

IdentifiersCVE-2009-3129CWE-119

CVE-2009-3129 is a client-side memory corruption vulnerability in Microsoft Excel and related Office components, including Excel 2002 SP3, Excel 2003 SP3, Excel 2007 SP1/SP2, Office 2004 and 2008 for Mac, the Open XML File Format Converter for Mac, Excel Viewer 2003 SP3, Excel Viewer SP1/SP2, and the Office Compatibility Pack for Word, Excel, and PowerPoint 2007 File Formats SP1/SP2. The flaw is triggered when Excel parses a malicious spreadsheet containing a FEATHEADER record with an invalid cbHdrData size value, causing an incorrect pointer offset during processing and resulting in memory corruption. A remote attacker can deliver a crafted Excel file, typically via spearphishing or other untrusted file-delivery channels, and achieve arbitrary code execution when the file is opened in a vulnerable application. The vulnerability is also referred to as the "Excel Featheader Record Memory Corruption Vulnerability."

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ANALYST BRIEF

Impact, mitigation & remediation

What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.

Impact

What an attacker gets, and what they’ve been doing with it.

Successful exploitation can result in arbitrary code execution in the security context of the user who opens the malicious spreadsheet. This enables installation and execution of malware, theft or modification of local data accessible to the user, and use of the compromised host as an initial foothold for further intrusion activity. Because this is a client-side Office parsing flaw, it is well suited for phishing-based initial access and has been observed in targeted intrusion activity.

Mitigation

If you can’t patch tonight, do this now.

Until patching is complete, reduce exposure by blocking or quarantining untrusted Excel attachments, especially from email and web downloads; disable or restrict opening spreadsheet files from untrusted sources using protected-view or equivalent controls where available; enforce least-privilege so users do not operate routinely with administrative rights; and use email/web filtering and attachment sandboxing to detect malicious Office documents. Organizations should also consider disabling or limiting legacy Office components and viewers that are no longer required.

Remediation

Patch, then assume compromise.

Apply the Microsoft security updates that address CVE-2009-3129 for all affected Microsoft Office, Excel Viewer, Compatibility Pack, and Mac Office products. Upgrade unsupported or legacy Office installations to supported versions that include the fix. Ensure all related components capable of parsing Excel files, including viewers and compatibility/converter packages, are patched because exploitation can occur through those components as well.
PUBLIC EXPLOITS

Exploits

No valid public exploits. Mallory filtered out 1 candidate as fakes, detection scripts, or README-only repos.

VALID 0 / 1 TOTALView more in app

All candidate exploits were filtered out by Mallory's validation.

EXPOSURE SURFACE

Affected products & vendors

Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.

VendorProductType
Microsoft CorporationExcelapplication
Microsoft CorporationExcel Viewerapplication
Microsoft CorporationOfficeapplication
Microsoft CorporationOpen Xml File Format Converterapplication

Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.

ACTIVITY FEED

Recent activity

6 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.

6 SOURCESView more in app
+2 more in the timeline
What this page doesn’t show

The version that knows your environment.

This page is what’s public. Mallory adds the parts that aren’t: which of your assets are affected, which adversaries are exploiting it right now, which detections to deploy, and what to do tonight.
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Exposure mapping

Query your assets running an affected version, and investigate the blast radius.

Threat actor evidence3

Every observed campaign linking this CVE to a named adversary.

Associated malware1

Malware families riding this exploit, with evidence and IOCs.

Detection signatures1

YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.

Vendor-by-vendor mapping

Cross-references every affected SKU, including bundled OEM variants.

Social activity

Community discussion across Reddit, Mastodon, and other social sources.

EXTERNAL REFERENCES
MITRE CVE
cve.org · CVE-2009-3129
NVD
nvd.nist.gov/vuln/detail/CVE-2009-3129
MITRE CWE · CWE-119
cwe.mitre.org
Patch
docs.microsoft.com/en-us/security-updates/securitybulletins/2009/ms09-067
Third Party Advisory
exploit-db.com/exploits/14706
Third Party Advisory
us-cert.gov/cas/techalerts/TA09-314A.html
Third Party Advisory
zerodayinitiative.com/advisories/ZDI-09-083
US Government Resource
cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2009-3129