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How CVE-2025-30381 Works
This vulnerability exploits an out-of-bounds read flaw in Microsoft Excel’s file parsing mechanism. When a maliciously crafted Excel document (.xlsx/.xls) is opened, the application fails to properly validate cell data ranges during spreadsheet rendering. This allows an attacker to read adjacent memory contents, potentially leaking sensitive information or enabling further exploitation via code execution. The corruption occurs when processing specially designed formulas that reference invalid sheet indexes, triggering improper memory access.
DailyCVE Form:
Platform: Microsoft Excel
Version: 2019/2021/365
Vulnerability: Out-of-bounds read
Severity: Critical
Date: 05/19/2025
What Undercode Say:
Exploitation:
- Craft malicious Excel file with corrupted formula references:
import openpyxl wb = openpyxl.Workbook() ws = wb.active ws['A1'] = "=SUM(INDIRECT('Sheet" + chr(0xFFFF) + "'!A1:A10'))" wb.save("exploit.xlsx") - Use memory dump tools to analyze leaked data:
!analyze -v !heap -p -a <corrupted_address>
Protection:
1. Apply Microsoft patch KB5035852:
wusa /update /kb:5035852 /quiet /norestart
2. Disable macro execution via Group Policy:
[HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\16.0\Excel] "VBAWarnings"=dword:00000002
3. Memory protection mitigations:
echo 2 > /proc/sys/kernel/randomize_va_space
Detection:
1. YARA rule for exploit files:
rule Excel_OOB_Read_CVE_2025_30381 {
strings:
$formula = /=\w+(.Sheet[\x80-\xFF]{2}/
condition:
$formula and filesize < 1MB
}
2. Audit log monitoring command:
Get-WinEvent -LogName "Microsoft Office Alerts" | Where-Object {$_.ID -eq 3007}
3. Network-based detection (Snort):
alert tcp any any -> any 445 (msg:"Excel OOB Read Attempt"; content:"|D0 CF 11 E0|"; depth:4; content:"|FD FF FF FF|"; within:1000;)
Sources:
Reported By: nvd.nist.gov
Extra Source Hub:
Undercode
