CVE-2024-52879: Insyde InsydeH2O Buffer Overflow Flaw

CVE-2024-52879 Overview

CVE-2024-52879 is a buffer over-read vulnerability in the Insyde InsydeH2O UEFI firmware. The flaw resides in the VariableRuntimeDxe driver, where the SmmUpdateVariablePropertySmi() System Management Mode (SMM) callback function uses StrCmp() to compare variable names. Because StrCmp() does not enforce a bounded length, processing a maliciously crafted variable name can read memory beyond the intended buffer. The issue is tracked under [CWE-126] (Buffer Over-read) and affects multiple InsydeH2O kernel branches from 5.2 through 5.7.

Critical Impact
An attacker leveraging the SMM callback can trigger an out-of-bounds memory read in firmware-privileged code, exposing sensitive SMM memory contents.

Affected Products

Insyde InsydeH2O kernel 5.2 before 05.29.50
Insyde InsydeH2O kernel 5.3 before 05.38.50, kernel 5.4 before 05.46.50, kernel 5.5 before 05.54.50
Insyde InsydeH2O kernel 5.6 before 05.61.50 and kernel 5.7 before 05.70.50

Discovery Timeline

2025-05-15 - CVE-2024-52879 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2024-52879

Vulnerability Analysis

The vulnerability resides in SmmUpdateVariablePropertySmi(), an SMM callback in the VariableRuntimeDxe driver. SMM callbacks execute in System Management Mode, the most privileged execution context on x86 platforms. The function compares incoming UEFI variable names with StrCmp(), a routine that walks both strings until it encounters a null terminator.

When attacker-controlled input lacks a proper null terminator within the expected buffer, StrCmp() continues reading adjacent SMRAM memory. This results in a buffer over-read classified as [CWE-126]. The leaked bytes may contain firmware secrets, pointers, or other state that should remain isolated within SMM.

Root Cause

The root cause is the use of an unbounded string comparison primitive on data whose length is not validated. Safer alternatives such as StrnCmp() with an explicit maximum length would constrain the read to the allocated buffer. The driver also fails to validate that input pointers and buffer sizes originate from outside SMRAM before dereferencing them in privileged context.

Attack Vector

Exploitation requires the ability to invoke the SMI handler with a crafted communication buffer. An attacker with appropriate local privileges or a chained vulnerability that allows triggering SMIs can supply a malformed variable name. The handler then executes StrCmp() against that input inside SMM and discloses memory contents through observable side effects or returned data. Successful exploitation undermines firmware isolation guarantees and can support follow-on attacks such as bypassing Secure Boot or persisting implants at the firmware layer.

Detection Methods for CVE-2024-52879

Indicators of Compromise

Unexpected SMI activity correlated with UEFI variable services on systems running vulnerable InsydeH2O kernel versions.
Firmware integrity baseline deviations reported by platform attestation or measured boot logs.
Crashes, hangs, or unexplained reboots tied to variable update operations during boot or runtime.

Detection Strategies

Inventory firmware versions across endpoints and compare against the fixed InsydeH2O kernel builds listed in the Insyde Security Advisory SA-2024016.
Use UEFI vulnerability scanners such as CHIPSEC to identify systems running vulnerable VariableRuntimeDxe modules.
Monitor endpoint telemetry for processes invoking UEFI variable APIs with anomalous variable name lengths or non-printable inputs.

Monitoring Recommendations

Enable measured boot and TPM-based remote attestation to detect unexpected firmware state changes.
Centralize firmware version, BIOS event log, and Secure Boot status data in a SIEM for fleet-wide review.
Track vendor advisories from Insyde Security Pledge for follow-up disclosures affecting the same kernel branches.

How to Mitigate CVE-2024-52879

Immediate Actions Required

Identify all systems whose OEM firmware is built on InsydeH2O kernel 5.2 through 5.7 and confirm the installed kernel revision.
Coordinate with platform OEMs to obtain firmware updates incorporating the fixed Insyde kernel versions.
Restrict local administrative access on affected systems until firmware updates are deployed, since SMI invocation typically requires elevated privileges.

Patch Information

Insyde has released fixed kernels: 05.29.50 for the 5.2 branch, 05.38.50 for 5.3, 05.46.50 for 5.4, 05.54.50 for 5.5, 05.61.50 for 5.6, and 05.70.50 for 5.7. Patches are delivered through OEM firmware updates rather than directly from Insyde. Refer to the Insyde Security Advisory SA-2024016 for the authoritative version mapping.

Workarounds

Enforce Secure Boot and BIOS administrator passwords to limit local attackers' ability to stage exploitation prerequisites.
Apply application allow-listing and least-privilege policies to reduce the likelihood of code execution that can issue arbitrary SMIs.
Where supported, enable platform features such as Intel Boot Guard and SMM protections (SMM_CODE_CHK_EN) to constrain SMM behavior pending firmware updates.

bash

# Identify InsydeH2O firmware version on Linux
sudo dmidecode -s bios-vendor
sudo dmidecode -s bios-version
sudo dmidecode -s bios-release-date

# On Windows (PowerShell)
Get-CimInstance -ClassName Win32_BIOS | Select-Object Manufacturer, SMBIOSBIOSVersion, ReleaseDate