CVE-2009-0557
Microsoft Office Object Record Corruption Vulnerability
Description
CVE-2009-0557 is an object record corruption vulnerability in Microsoft Office that allows remote attackers to execute arbitrary code via a crafted Excel file containing a malformed record object. The flaw occurs when Excel's file parser processes a corrupted record structure, leading to memory corruption that can be exploited to execute attacker-controlled code in the context of the logged-in user. CISA has added CVE-2009-0557 to its Known Exploited Vulnerabilities catalog, and with an EPSS score of 86.4% (99th percentile), this vulnerability has a very high probability of exploitation.
KEV Information
CVSS Score
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:HOpen in CalculatorAffected Products
| Vendor | Product | Version |
|---|---|---|
| microsoft | office | 2000; 2003; 2004; 2007; 2008; xp |
| microsoft | office compatibility pack | 2007 |
| microsoft | office excel viewer | -; 2003 |
| microsoft | office sharepoint server | 2007 |
| microsoft | open xml file format converter | - |
Multiple CVSS Assessments
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
References
- http://osvdb.org/54953(Broken Link)
- http://www.securityfocus.com/bid/35241(Broken Link, Third Party Advisory, VDB Entry)
- http://www.securitytracker.com/id?1022351(Broken Link, Third Party Advisory, VDB Entry)
- http://www.us-cert.gov/cas/techalerts/TA09-160A.html(Broken Link, Third Party Advisory, US Government Resource)
- http://www.vupen.com/english/advisories/2009/1540(Broken Link)
- https://docs.microsoft.com/en-us/security-updates/securitybulletins/2009/ms09-021(Patch, Vendor Advisory)
- https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A5564(Broken Link)
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2009-0557(US Government Resource)
Weakness Type
CWE-119: Improper Restriction of Operations within the Bounds of a Memory Buffer
CVE-2009-0557 exploits a memory corruption condition in Microsoft Excel's record parsing routines, where the application fails to properly validate and restrict memory operations when processing malformed record objects within Excel files. The corrupted record data causes operations that exceed memory buffer boundaries, enabling arbitrary code execution.
Learn more: CWE-119 — Improper Restriction of Operations within the Bounds of a Memory Buffer
Impact Analysis
CVE-2009-0557 is remotely exploitable through a crafted Excel file — an attacker needs only to deliver a malicious spreadsheet to a victim via email, web download, or file sharing. No authentication is required, though user interaction is needed to open the file. Successful exploitation leads to arbitrary code execution with the privileges of the current user, placing confidentiality, integrity, and availability at full risk. An attacker can steal financial data, install keyloggers or banking trojans, or establish persistent backdoor access. The EPSS score of 86.4% (99th percentile) indicates a very high probability of exploitation. Excel spreadsheets are among the most commonly shared business documents, making this vulnerability particularly effective for social engineering campaigns targeting financial departments and business analysts.
Exploit Maturity
CISA has confirmed active exploitation of CVE-2009-0557 in the wild by adding it to the Known Exploited Vulnerabilities catalog on June 8, 2022. The EPSS score of 86.4% places this vulnerability in the 99th percentile, indicating a very high probability of exploitation. The Excel-based attack vector is particularly attractive for targeted attacks against financial institutions, accounting firms, and business organizations where Excel files are routinely exchanged. No specific ransomware association has been reported, but the reliable remote code execution capability through a common business document format makes it suitable for diverse attack campaigns.
Remediation
- Apply Microsoft security updates immediately: Install the relevant patches for Microsoft Office and Excel as directed by the CISA KEV required action to address the object record corruption vulnerability.
- Upgrade legacy Office installations: If running Office 2000, 2003, or 2007, upgrade to a currently supported Office version with modern exploit mitigations such as ASLR, DEP, and sandboxed file parsing.
- Enable Protected View for Excel files: Ensure Microsoft Office Protected View is enabled for all Excel files received from external sources, which opens spreadsheets in a restricted sandbox.
- Deploy email attachment scanning for Excel files: Configure email security gateways to perform deep content inspection of Excel files, scanning for malformed record objects and known exploit signatures.
- Monitor for suspicious Excel process behavior: Configure endpoint detection to alert on unusual Excel process activity such as unexpected child process creation, network connections from excel.exe, or memory corruption indicators.
Technical Details
CVE-2009-0557 is a memory corruption vulnerability in Microsoft Excel triggered by a malformed record object within an Excel file. The Excel file format (particularly the older binary XLS format) uses a record-based structure where each record contains a type identifier and associated data. When Excel's parser encounters a crafted record with corrupted or inconsistent data, the resulting memory operations exceed the bounds of allocated buffers, classified under CWE-119. This memory corruption can overwrite critical data structures including function pointers or heap metadata, enabling the attacker to redirect program execution. The vulnerability specifically targets the record parsing layer, which processes the fundamental structural elements of the spreadsheet file, making the exploit reliable regardless of the spreadsheet's visible content.
Frequently Asked Questions
Is CVE-2009-0557 being actively exploited?
Yes. CISA has confirmed active exploitation by adding CVE-2009-0557 to the Known Exploited Vulnerabilities catalog. The EPSS score of 86.4% in the 99th percentile indicates a very high probability of ongoing exploitation through malicious Excel files.
What products are affected by CVE-2009-0557?
CVE-2009-0557 affects Microsoft Office, specifically the Excel component's record parsing routines. Multiple Office versions including Office 2000, 2003, and 2007 are known to be vulnerable.
How do I fix CVE-2009-0557?
Apply the Microsoft security updates for Office and upgrade to a currently supported version. Enable Protected View for all externally received Excel files and deploy email attachment scanning to detect malicious spreadsheets.
How severe is CVE-2009-0557?
CVE-2009-0557 is a severe vulnerability with an EPSS score in the 99th percentile, enabling remote code execution through crafted Excel files. The prevalence of Excel spreadsheets in business workflows and the targeting of financial data make this vulnerability particularly dangerous for enterprise environments.
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