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The DEF CON 32 conference took place at the Las Vegas Convention Center and featured presentations on cybersecurity and technology, which are now available on the organization’s YouTube channel.
Recent findings have identified a vulnerability in fully patched Windows 11 systems that allows attackers to install custom rootkits, which can bypass endpoint security and maintain persistence on compromised systems. This vulnerability is linked to a downgrade attack technique demonstrated by SafeBreach researcher Alon Leviev at Black Hat USA 2024, using an exploit tool called Windows Downdate. This tool enables an attacker with administrative access to manipulate the Windows Update process, reverting patched components to vulnerable states.
Leviev's demonstration showed that even systems using virtualization-based security (VBS) are at risk, as he could downgrade VBS features and expose previously fixed privilege escalation vulnerabilities. Microsoft has patched two vulnerabilities (CVE-2024-21302 and CVE-2024-38202) but has not addressed the core issue of the downgrade capability. Microsoft maintains that the ability for an admin-level user to gain kernel code execution does not cross a security boundary.
Leviev released details of a new downgrade attack on October 26, using the Windows Downdate tool to revive a driver signature enforcement bypass attack. He categorized this flaw as False File Immutability (FFI), exploiting incorrect assumptions about file immutability. He noted that downgrading specific OS modules, like CI.dll, allows exploitation even with VBS enabled. Tim Peck from Securonix highlighted that the attacks exploit Windows' failure to validate DLL version numbers properly, enabling the use of outdated, vulnerable files.
Microsoft is actively developing mitigations against these risks, including a security update to revoke outdated VBS system files, although specific measures and timelines are not yet disclosed.
Cybersecurity experts have discovered a method that allows cybercriminals to bypass Windows security features, specifically Driver Signature Enforcement (DSE), enabling the installation of rootkits on fully updated systems. Alon Leviev from SafeBreach reported that the exploit involves downgrading specific Windows kernel components, making Windows 11 devices particularly vulnerable. Despite notifying Microsoft, no fix has been implemented, as the company stated the vulnerability does not breach a “security boundary” since administrator access is required for exploitation.
Leviev presented this vulnerability at the Black Hat and DEF CON 2024 conferences, introducing a tool called Windows Downdate that can reactivate previously patched vulnerabilities. He demonstrated downgrading components on Windows 11 to bypass DSE and install rootkits that disable security software. A key part of his attack involved replacing the ci.dll file with an unpatched version, which requires a system restart and disguises the action as a routine update. Leviev also showed methods to disable Virtualization-Based Security (VBS) by modifying settings and files.
Microsoft is working on a solution to block outdated system files and prevent downgrade attacks, but the timeline for this fix is uncertain due to the need for thorough testing. Leviev advises organizations to remain vigilant against downgrade attacks until a resolution is available.
A newly identified attack technique poses a risk to fully patched Windows systems by circumventing Microsoft's Driver Signature Enforcement (DSE), potentially enabling operating system downgrade attacks that allow malicious actors to load unsigned kernel drivers. This vulnerability is linked to two privilege escalation flaws in the Windows update mechanism, identified as CVE-2024-21302 and CVE-2024-38202, which can be exploited to revert updated systems to earlier versions with unpatched security weaknesses. A tool called Windows Downdate can hijack the Windows Update process, facilitating undetectable downgrades of critical OS components. The exploit takes advantage of a race condition to replace a verified security catalog file with a malicious version, allowing the loading of an unsigned kernel driver. The DSE bypass can be executed by downgrading the "ci.dll" library, but can be thwarted if Virtualization-Based Security (VBS) is active on the host. Attackers can disable VBS by manipulating registry keys, and the attack fails only if VBS is enabled with a UEFI lock and a "Mandatory" flag, which prevents booting if VBS files are corrupted. Microsoft has addressed the vulnerabilities in August and October 2024.
SafeBreach security researcher Alon Leviev has identified a vulnerability in the Windows operating system that allows attackers to downgrade kernel components, bypassing security measures like Driver Signature Enforcement (DSE). This vulnerability enables the installation of rootkits on fully patched systems. Leviev demonstrated that attackers can manipulate the Windows Update process to introduce outdated components without altering the system's patched status. He introduced a tool called Windows Downdate, which allows the creation of custom downgrades, exposing updated systems to previously patched vulnerabilities. Leviev's method, named "ItsNotASecurityBoundary," exploits a flaw in the DSE, allowing unsigned kernel drivers to be loaded and facilitating the deployment of rootkit malware. Despite Microsoft addressing the privilege escalation aspect of this vulnerability, it does not protect against downgrade attacks. Leviev's research shows that attackers can replace the 'ci.dll' file responsible for enforcing DSE with an unpatched version during the Windows Update process, thereby circumventing protections. He also discussed methods to disable Microsoft's Virtualization-based Security (VBS), which is designed to protect critical resources, by modifying registry keys. Leviev emphasizes the need for endpoint security tools to monitor downgrade procedures to mitigate these risks.
A new tool called "Windows Downdate," created by security researcher Alon Leviev, allows users to revert their Windows systems to older, vulnerable versions. It is available for download on GitHub and is compatible with Windows 10, Windows 11, and Windows Server. The tool enables attackers to downgrade critical components of the operating system, reopening previously patched security flaws without user awareness. The vulnerabilities targeted by this tool are CVE-2024-38202 and CVE-2024-21302. While Microsoft has addressed CVE-2024-21302, CVE-2024-38202 is still under scrutiny. Windows Downdate is intended for research and testing, requiring user initiation to execute a downgrade, but it poses risks of malicious adaptations. Users are advised to exercise caution with unknown emails and links, avoid untrusted downloads, and maintain updated antivirus software.
At the Black Hat 2024 conference, SafeBreach researcher Anon Leviev introduced a tool called Windows Downdate, which can silently reverse security patches on Windows 10, Windows 11, and Windows Server systems. This open-source Python program allows users to execute downgrade attacks, reintroducing previously patched vulnerabilities, including CVE-2024-21302 and CVE-2024-38202. The tool can bypass Windows Update, making it appear that the system is fully updated while it has been downgraded. Leviev demonstrated its use by reverting the Hyper-V hypervisor and other Windows components to earlier versions. Microsoft released a security update on August 7 for CVE-2024-21302 but has not yet issued a patch for CVE-2024-38202. Until a patch is available, Microsoft recommends users follow specific security guidelines to mitigate risks.
