How severe is CVE-2009-0100?

CVE-2009-0100 has a CVSS 2.0 base score of 9.3, rated critical severity.

Is CVE-2009-0100 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 29% (98th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2009-0100?

CVE-2009-0100 primarily affects Microsoft Office. In total, 9 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2009-0100?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2009-0100 published?

CVE-2009-0100 was published on 2009-04-15 and last updated on 2026-06-16.

CVE-2009-0100

CVE-2009-0100 is a critical-severity vulnerability in Microsoft Office with a CVSS 2.0 base score of 9.3. Its EPSS exploit-prediction score of 29% places it in the 98th percentile, indicating an elevated likelihood of exploitation. The underlying weakness is classified as CWE-399.

Key facts

Severity: Critical (CVSS 2.0 base score 9.3)
EPSS exploit prediction: 29% (98th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-399
Affected product: Microsoft Office
Published: 2009-04-15
Last modified: 2026-06-16

Description

Microsoft Office Excel 2000 SP3, 2002 SP3, 2003 SP3, and 2007 SP1; Excel in Microsoft Office 2004 and 2008 for Mac; Microsoft Office Excel Viewer and Excel Viewer 2003 SP3; and Microsoft Office Compatibility Pack for Word, Excel, and PowerPoint 2007 File Formats SP1 do not properly parse the Excel spreadsheet file format, which allows remote attackers to execute arbitrary code via a crafted spreadsheet that contains a malformed object with "an offset and a two-byte value" that trigger a memory calculation error, aka "Memory Corruption Vulnerability."

Frequently asked questions

What is CVE-2009-0100?: Microsoft Office Excel 2000 SP3, 2002 SP3, 2003 SP3, and 2007 SP1; Excel in Microsoft Office 2004 and 2008 for Mac; Microsoft Office Excel Viewer and Excel Viewer 2003 SP3; and Microsoft Office Compatibility Pack for Word, Excel, and PowerPoint 2007 File Formats SP1 do not properly parse the Excel spreadsheet file format, which allows remote attackers to execute arbitrary code via a crafted spreadsheet that contains a malformed object with "an offset and a two-byte value" that trigger a memory calculation error, aka "Memory Corruption Vulnerability."
How severe is CVE-2009-0100?: CVE-2009-0100 has a CVSS 2.0 base score of 9.3, rated critical severity.
Is CVE-2009-0100 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 29% (98th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2009-0100?: CVE-2009-0100 primarily affects Microsoft Office. In total, 9 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2009-0100?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2009-0100 published?: CVE-2009-0100 was published on 2009-04-15 and last updated on 2026-06-16.

References

Affected products (9)

cpe:2.3:a:microsoft:office:2004:*:mac:*:*:*:*:*
cpe:2.3:a:microsoft:office:2008:*:mac:*:*:*:*:*
cpe:2.3:a:microsoft:office_compatibility_pack_for_word_excel_ppt_2007:*:sp1:*:*:*:*:*:*
cpe:2.3:a:microsoft:office_excel:2000:sp3:*:*:*:*:*:*
cpe:2.3:a:microsoft:office_excel:2002:sp3:*:*:*:*:*:*
cpe:2.3:a:microsoft:office_excel:2003:sp3:*:*:*:*:*:*
cpe:2.3:a:microsoft:office_excel:2007:sp1:*:*:*:*:*:*
cpe:2.3:a:microsoft:office_excel_viewer:*:*:*:*:*:*:*:*
cpe:2.3:a:microsoft:office_excel_viewer:2003:sp3:*:*:*:*:*:*

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CVE-2014-4121 — Critical (CVSS 10.0): Microsoft .NET Framework 2.0 SP2, 3.5, 3.5.1, 4, 4.5, 4.5.1, and 4.5.2 does not properly parse internationalized…
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