CVE-2024-52878 Overview
CVE-2024-52878 is a buffer over-read vulnerability [CWE-126] in the Insyde InsydeH2O UEFI firmware. The flaw resides in the VariableRuntimeDxe driver, specifically within the VariableServicesSetVariable() function. The function uses StrSize(), StrLen(), and StrCmp() on variable name input without proper bounds validation. Attackers can trigger reads beyond allocated buffers by invoking gRT->SetVariable(), SmmSetSensitiveVariable(), or SmmInternalSetVariable() from System Management Mode (SMM). The issue affects InsydeH2O kernel branches 5.2 through 5.7 prior to their respective fixed releases.
Critical Impact
A buffer over-read in low-level UEFI firmware can leak sensitive memory contents from SMM and runtime services, undermining platform integrity guarantees.
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
- Insyde InsydeH2O kernel 5.5 before 05.54.50, kernel 5.6 before 05.61.50, kernel 5.7 before 05.70.50
Discovery Timeline
- 2025-05-15 - CVE-2024-52878 published to NVD
- 2025-08-15 - Last updated in NVD database
Technical Details for CVE-2024-52878
Vulnerability Analysis
The vulnerability exists in the VariableRuntimeDxe driver, a core UEFI component responsible for handling UEFI variable services. The function VariableServicesSetVariable() processes variable names passed in from runtime callers via gRT->SetVariable() and from SMM callers via SmmSetSensitiveVariable() or SmmInternalSetVariable(). Inside this function, string handling primitives StrSize(), StrLen(), and StrCmp() traverse the supplied variable name buffer. These routines scan memory until they locate a null terminator, but the implementation does not validate that the supplied buffer contains a terminator within its declared length. Attackers controlling the variable name input can cause the routines to read past the end of the allocated buffer.
Root Cause
The root cause is missing bounds enforcement on caller-supplied variable name buffers before invoking length-based string operations. StrSize() and StrLen() rely on null-terminated semantics, and StrCmp() continues comparison until a mismatch or terminator. When the caller supplies a non-terminated or truncated name, the routines read adjacent memory, classifying this as a buffer over-read [CWE-126].
Attack Vector
An attacker requires the ability to invoke UEFI variable services. SMM callers (SmmSetSensitiveVariable(), SmmInternalSetVariable()) imply local privileged code execution in System Management Mode, while gRT->SetVariable() is reachable from runtime contexts including the operating system. Successful exploitation can disclose firmware memory contents to the attacker, potentially exposing keys, configuration data, or breaking SMM isolation assumptions. The CVSS vector indicates a confidentiality-only impact with no effect on integrity or availability.
No public proof-of-concept code or exploit modules are currently available for this issue. Refer to the Insyde Advisory SA-2024016 for vendor-supplied technical details.
Detection Methods for CVE-2024-52878
Indicators of Compromise
- Firmware versions reporting InsydeH2O kernel builds below the patched releases listed in the vendor advisory.
- Unexpected UEFI variable creation or modification events originating from unsigned or untrusted runtime drivers.
- Anomalous SMM handler invocations targeting variable services from non-platform code paths.
Detection Strategies
- Inventory firmware versions across the fleet and compare against the fixed kernel revisions published in Insyde Advisory SA-2024016.
- Use UEFI integrity tooling such as CHIPSEC to capture variable contents and validate driver versions for VariableRuntimeDxe.
- Correlate firmware update telemetry with vendor OEM BIOS releases to confirm patch deployment.
Monitoring Recommendations
- Monitor endpoint platforms for OEM BIOS update notifications referencing Insyde firmware components.
- Track operating system event logs for UEFI variable write failures or unusual SetVariable activity from kernel drivers.
- Audit privileged local accounts that could load drivers capable of issuing runtime service calls.
How to Mitigate CVE-2024-52878
Immediate Actions Required
- Identify systems running Insyde InsydeH2O firmware on kernel branches 5.2 through 5.7 below the fixed versions.
- Coordinate with OEM hardware vendors to obtain BIOS updates that integrate the patched InsydeH2O kernel.
- Restrict local administrative access to limit the population of users able to load drivers that invoke runtime variable services.
Patch Information
Insyde has released fixed firmware kernels: 05.29.50 (kernel 5.2), 05.38.50 (kernel 5.3), 05.46.50 (kernel 5.4), 05.54.50 (kernel 5.5), 05.61.50 (kernel 5.6), and 05.70.50 (kernel 5.7). Patches must be obtained and deployed through the system OEM. See the Insyde Security Pledge and Insyde Advisory SA-2024016 for full version mapping.
Workarounds
- Enable UEFI Secure Boot and BIOS administrator passwords to reduce the attack surface for untrusted code reaching variable services.
- Apply OS-level driver signing enforcement to prevent unsigned drivers from invoking SetVariable calls.
- Where supported, restrict SMM communication buffers and enable SMM protections (SMM_BWP, SMM Supervisor) provided by platform vendors.
# Configuration example: enumerate UEFI firmware version on Linux to validate patch state
sudo dmidecode -s bios-version
sudo dmidecode -s bios-release-date
sudo dmidecode -t bios | grep -i 'Vendor\|Version\|Release Date'
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
