UEBI
A flaw exposing UEFI Secure Boot vulnerabilities. Learn how attackers exploit it...
Researchers have identified an exceptionally critical vulnerability, CVE-2024-7344, that undermines UEFI Secure Boot, a cornerstone security mechanism designed to ensure the integrity of the system boot process. This vulnerability enables malicious code execution during the boot sequence, even when Secure Boot is active, jeopardizing countless modern systems' security posture. The impacted systems span a broad spectrum of UEFI-based devices, significantly elevating the risks of deploying UEFI bootkits such as Bootkitty or BlackLotus.
The ramifications of this discovery are profound. Secure Boot, integral to protecting the boot chain, becomes ineffective when exploited, leading to unauthorized code execution. This raises severe security concerns across industries relying on UEFI-based devices, as attackers can compromise systems without triggering conventional security mechanisms.
### In-Depth Analysis of CVE-2024-7344
#### Vulnerability Context
The vulnerability emanates from a defective UEFI application, signed by Microsoft’s widely trusted Microsoft Corporation UEFI CA 2011 certificate. This enables attackers to circumvent Secure Boot by executing unsigned binaries during startup. The vulnerability affects multiple recovery software suites, including but not limited to:
- **Howyar SysReturn** (versions prior to 10.2.023\_20240919)
- **Greenware GreenGuard** (versions prior to 10.2.023-20240927)
- **Radix SmartRecovery** (versions prior to 11.2.023-20240927)
- **Sanfong EZ-back System** (versions prior to 10.3.024-20241127)
- **WASAY eRecoveryRX** (versions prior to 8.4.022-20241127)
- **CES NeoImpact** (versions prior to 10.1.024-20241127)
- **SignalComputer HDD King** (versions prior to 10.3.021-20241127)
#### Root Cause and Technical Insights
The crux of the vulnerability lies in the usage of a custom PE loader, bypassing standard UEFI functions such as `LoadImage` and `StartImage`. This flawed implementation allows the execution of unsigned UEFI binaries from a specifically crafted file named `cloak.dat`, rendering Secure Boot policies ineffective.
#### Exploitation Mechanism
Meticulous investigation revealed that the `cloak.dat` file, part of the vulnerable recovery software, contains an encrypted UEFI binary. Instead of leveraging UEFI’s integrity checks, the custom loader decrypts and executes the binary directly. The steps to exploit this vulnerability include:
1. **Replacing the Bootloader**: Attackers substitute the system’s default bootloader with the compromised `reloader.efi` binary.
2. **Deploying Malicious Payloads**: A crafted `cloak.dat` file containing unsigned binaries is placed on the EFI System Partition (ESP).
3. **Executing the Payload**: Upon reboot, the malicious binary executes without adherence to Secure Boot policies.
The attack requires elevated privileges (e.g., local administrator rights on Windows or root access on Linux) but is feasible across systems trusting Microsoft’s third-party UEFI certificate.
### UEFI Secure Boot: A Comprehensive Overview
UEFI Secure Boot ensures the integrity of the boot process by validating binaries against two key databases:
1. **db**: Lists trusted certificates and hashes authorized for execution.
2. **dbx**: Enumerates revoked certificates and hashes, explicitly forbidding their execution.
Most UEFI devices ship with Microsoft’s certificates preloaded to maintain compatibility with major operating systems. However, this reliance on Microsoft centralizes control over boot security, exposing potential systemic vulnerabilities when these certificates are compromised.
### Coordinated Disclosure and Remediation Timeline
The responsible disclosure process ensured swift vendor responses and mitigation measures. Key milestones include:
- **2024-07-08**: Discovery of the vulnerability by researchers.
- **2024-07-09**: Reporting to CERT Coordination Center (CERT/CC).
- **2024-08-05**: CERT/CC engages affected vendors.
- **2024-08-20**: Initial patches reviewed; additional flaws identified.
- **2024-09-23**: Disclosure rescheduled to align with remediation timelines.
- **2025-01-14**: Vulnerable binaries revoked in Microsoft’s Patch Tuesday update.
This coordinated effort underscores the importance of collaboration between researchers, CERTs, and vendors in addressing security threats efficiently.
### Mitigation Strategies and Detection Mechanisms
#### Applying UEFI Revocations
Users are strongly advised to update their systems with the latest UEFI revocations from Microsoft. Verification steps include:
**Windows Systems**:
```powershell
[System.Text.Encoding]::ASCII.GetString((Get-SecureBootUEFI db).bytes) -match 'Microsoft Corporation UEFI CA 2011'
[BitConverter]::ToString((Get-SecureBootUEFI dbx).bytes) -replace '-' -match 'cdb7c90d3ab8833d5324f5d8516d41fa990b9ca721fe643fffaef9057d9f9e48'
```
**Linux Systems**:
```bash
dbxtool --list | grep 'cdb7c90d3ab8833d5324f5d8516d41fa990b9ca721fe643fffaef9057d9f9e48'
```
#### Strengthening UEFI Configurations
1. **Customized Secure Boot Policies**: Tailor Secure Boot settings to restrict unauthorized access.
2. **EFI Partition Protections**: Limit access to the EFI System Partition through managed permissions.
3. **Remote Attestation**: Leverage TPM for remote validation of boot configurations.
### Implications and Recommendations
CVE-2024-7344 exemplifies systemic vulnerabilities in the UEFI ecosystem, driven by opaque third-party signing processes. To enhance security, stakeholders must advocate for greater transparency and stringent review protocols in UEFI application signing. Microsoft’s upcoming UEFI certificate updates provide a pivotal opportunity to address these challenges.
For detailed inquiries, contact [threatintel@researchteam.com](mailto\:threatintel@researchteam.com) or visit [Threat Intelligence page](https://www.researchteam.com).
