Lenovo System Management Mode Buffer Overflow (CVE-2025-4423): Brief Summary and Technical Details

This post provides a brief summary of CVE-2025-4423, a high-severity buffer overflow in Lenovo all-in-one desktop firmware System Management Mode (SMM). It covers technical details, affected products, and vendor security history based on available public sources.
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ZeroPath CVE Analysis

2025-07-29

Lenovo System Management Mode Buffer Overflow (CVE-2025-4423): Brief Summary and Technical Details
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Introduction

Attackers with local access to Lenovo all-in-one desktops can leverage a firmware flaw to achieve deep persistence and bypass security controls at the hardware level. CVE-2025-4423 is one of six high-impact vulnerabilities in Lenovo's System Management Mode (SMM) firmware, enabling memory corruption that can survive OS reinstalls and evade traditional detection.

About the involved parties:

  • Lenovo is a global leader in PC manufacturing, with a vast product portfolio spanning desktops, laptops, and enterprise devices. Their systems are widely deployed in both consumer and business environments, making vulnerabilities in their firmware especially impactful.
  • Insyde Software is a major supplier of UEFI firmware to OEMs, including Lenovo. Flaws in Insyde's codebase have affected multiple vendors, amplifying the reach of firmware vulnerabilities like CVE-2025-4423.

Technical Information

CVE-2025-4423 is a buffer overflow vulnerability (CWE-119) in the System Management Mode (SMM) firmware of certain Lenovo all-in-one desktops. The flaw arises from improper restriction of operations within the bounds of a memory buffer in SMM routines. Exploitation requires local or physical access to the device. An attacker can supply crafted input that overruns the intended buffer, corrupting SMM memory. This can allow modification of UEFI variables and installation of persistent malware that operates below the operating system, evading most endpoint security controls.

This vulnerability is part of a cluster of six SMM-related flaws (CVE-2025-4421 to CVE-2025-4426) identified by Binarly researchers. All six are associated with Insyde-based firmware used by Lenovo. The exploitation complexity is high, as it requires detailed knowledge of firmware internals and privileged or physical access. No public code snippets or proof of concept are available for this specific CVE.

Affected Systems and Versions

  • Products: Lenovo all-in-one desktop models using Insyde-based firmware
  • Advisory: LEN-201013
  • CVE Range: CVE-2025-4421 through CVE-2025-4426
  • Specific affected models and firmware versions: Refer to Lenovo's official advisory for the complete list of impacted products and firmware versions.

Vendor Security History

Lenovo has previously addressed similar firmware vulnerabilities, including buffer overflows and SMM issues (e.g., CVE-2025-4657). Their patch response to CVE-2025-4423 was coordinated with Binarly and included timely advisories and firmware updates. However, reliance on third-party BIOS vendors like Insyde has contributed to recurring vulnerabilities across Lenovo's product lines. Insyde's firmware has been implicated in multiple cross-vendor security advisories, highlighting systemic risks in firmware supply chains.

References

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