CVE-2024-28896 Overview
CVE-2024-28896 is a Secure Boot security feature bypass vulnerability affecting Microsoft Windows and Windows Server. Microsoft disclosed the flaw on April 9, 2024 as part of its Patch Tuesday release cycle. The issue is rooted in a heap-based buffer overflow condition [CWE-122] in Secure Boot components, allowing an attacker on an adjacent network to bypass Secure Boot protections. Successful exploitation compromises the integrity of the boot chain and can lead to loss of confidentiality, integrity, and availability on the affected host. The vulnerability impacts every supported Windows client build from Windows 10 1507 through Windows 11 23H2, and all supported Windows Server releases from Server 2012 through Server 2022 23H2.
Critical Impact
An adjacent-network attacker who bypasses Secure Boot can undermine boot-time integrity checks, enabling persistent pre-OS code that survives standard remediation.
Affected Products
- Microsoft Windows 10 (1507, 1607, 1809, 21H2, 22H2)
- Microsoft Windows 11 (21H2, 22H2, 23H2)
- Microsoft Windows Server 2012, 2016, 2019, 2022, and 2022 23H2
Discovery Timeline
- 2024-04-09 - CVE-2024-28896 published to NVD and addressed by Microsoft
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2024-28896
Vulnerability Analysis
CVE-2024-28896 is classified as a Secure Boot Bypass driven by a heap-based buffer overflow [CWE-122]. Secure Boot is the UEFI feature that validates firmware and bootloader signatures before handing execution to the Windows boot manager. A flaw in the code that parses boot-related data structures allows attacker-controlled input to overflow a heap buffer during the boot validation path. This corrupts memory used to enforce signature and policy checks, letting unsigned or tampered code execute earlier in the chain than Secure Boot should permit.
The attack vector is Adjacent Network, meaning the attacker must have logical access to the same network segment as the target, for example through PXE, Windows Deployment Services, or a compromised device on the LAN. Attack complexity is High: exploitation depends on specific boot-time conditions and precise heap manipulation. No user interaction or prior authentication is required. An EPSS score of 0.951% indicates limited observed exploitation activity to date.
Root Cause
The root cause is insufficient bounds checking on data consumed by Secure Boot components during the pre-OS boot phase. When oversized or malformed input reaches the vulnerable parser, adjacent heap metadata and function state are overwritten, subverting the integrity checks Secure Boot is designed to enforce.
Attack Vector
An attacker positioned on the adjacent network supplies a crafted payload consumed during boot, most plausibly through network boot services or a rogue update path reachable at the link-local layer. Because the flaw executes before the operating system has fully initialized, endpoint defenses running in Windows have no runtime context at the moment of compromise. Successful exploitation can install a bootkit that persists across reinstalls and provides tamper-resistant control of the host. See the Microsoft CVE-2024-28896 Advisory for vendor guidance.
Detection Methods for CVE-2024-28896
Indicators of Compromise
- Unexpected changes to UEFI variables, boot order entries, or the BootOrder and BootXXXX NVRAM values.
- Measured Boot logs (TPM PCR values) that deviate from a known-good baseline for the platform.
- Unsigned or unknown modules appearing in the boot chain reported by Windows Defender System Guard.
Detection Strategies
- Compare TPM attestation results against a hardware-vetted baseline using Device Health Attestation or an equivalent measured-boot verifier.
- Alert on hosts reporting SecureBoot disabled or in Setup Mode where policy requires User Mode enforcement.
- Monitor for anomalous PXE, DHCP, or WDS traffic from unmanaged devices on segments containing domain-joined endpoints.
Monitoring Recommendations
- Ingest Windows Event Log channels Microsoft-Windows-Kernel-Boot and Microsoft-Windows-CodeIntegrity into your SIEM for boot-time integrity events.
- Track firmware and Secure Boot DBX revocation list versions across the fleet to confirm patch propagation.
- Baseline network boot services and alert on rogue TFTP or PXE responders on client subnets.
How to Mitigate CVE-2024-28896
Immediate Actions Required
- Apply Microsoft's April 2024 security updates to all affected Windows and Windows Server builds. Refer to the Microsoft CVE-2024-28896 Advisory for the KB mapped to each build.
- Verify Secure Boot is enabled and enforcing User Mode on every managed endpoint after patching.
- Restrict PXE and network boot services to authenticated, segmented VLANs and disable them where not required.
Patch Information
Microsoft released fixes for CVE-2024-28896 on April 9, 2024 for all supported Windows client and server versions listed above. Patching requires both the OS cumulative update and, on some platforms, an updated Secure Boot DBX to revoke vulnerable bootloader components. Confirm both the OS build number and the UEFI revocation list are current after deployment.
Workarounds
- Disable network boot (PXE) at the firmware level on hosts that do not require it.
- Enforce 802.1X on wired segments to prevent unauthorized adjacent-network access to bootable clients.
- Require BitLocker with TPM+PIN so that any tampering with the boot chain triggers recovery-key prompts and detection.
# Verify Secure Boot state and UEFI configuration on Windows
Confirm-SecureBootUEFI
Get-SecureBootPolicy
# Confirm the DBX revocation list has been updated post-patch
[System.Text.Encoding]::ASCII.GetString((Get-SecureBootUEFI dbx).Bytes) | Select-String -Pattern 'Microsoft'
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
