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How CVE-2025-30379 Works
This vulnerability stems from improper memory handling in Microsoft Excel when processing specially crafted spreadsheet files. An attacker can exploit a use-after-free (UAF) condition by manipulating Excel’s object reference tracking. When a malicious file is opened, Excel fails to validate pointer references after certain operations, leading to arbitrary code execution under the victim’s privileges. The exploit chain involves:
1. A malformed Excel formula triggers an incorrect memory deallocation.
2. The freed memory is reused for a controlled object (e.g., a formula handler).
3. Attacker-supplied shellcode is executed via heap grooming or ROP chains.
DailyCVE Form:
Platform: Microsoft Excel
Version: 2019/2021/365
Vulnerability: Memory Corruption
Severity: Critical
Date: 05/19/2025
What Undercode Say:
Exploitation:
- Craft a malicious XLSX file with embedded VBA or formula arrays to trigger UAF.
- Use heap-spraying techniques to position shellcode in predictable memory regions.
- Leverage Excel’s legacy formula parser (e.g., `=HYPERLINK()` with crafted arguments).
Protection:
- Apply Microsoft’s patch KB5034856 or disable macro execution.
- Enable Attack Surface Reduction (ASR) rules to block Office child processes.
- Use Group Policy to restrict Excel’s dynamic data exchange (DDE) protocols.
Detection Commands:
Get-WinEvent -LogName "Microsoft Office Alerts" | Where-Object { $_.Message -match "CVE-2025-30379" }
Mitigation Script (PowerShell):
Set-ItemProperty -Path "HKLM:\SOFTWARE\Policies\Microsoft\Office\16.0\excel\security" -Name "DisableUnsafeLocations" -Value 1
Exploit PoC (Conceptual):
import openpyxl
wb = openpyxl.Workbook()
ws = wb.active
ws["A1"] = "=IFERROR(HYPERLINK('malicious_payload'), '')"
wb.save("exploit.xlsx")
References:
- Microsoft Advisory
- CVSS:4.0 AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H (9.8 Critical)
- CWE-416: Use After Free
Sources:
Reported By: nvd.nist.gov
Extra Source Hub:
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