CVE-2021-46756 Explained : Impact and Mitigation

CVE-2021-46756 is a vulnerability related to insufficient validation of inputs in the ASP bootloader of AMD processors, potentially leading to denial of service and loss of integrity.

Understanding CVE-2021-46756

What is CVE-2021-46756?

The vulnerability stems from inadequate input validation in SVC_MAP_USER_STACK in the ASP bootloader, which could be exploited by an attacker using a malicious Uapp or ABL to send malformed syscalls, resulting in a denial of service and integrity compromise.

The Impact of CVE-2021-46756

The impact of this vulnerability includes the potential for a denial of service attack and the compromise of system integrity, posing a significant threat to affected AMD processors.

Technical Details of CVE-2021-46756

Vulnerability Description

Insufficient validation of inputs in SVC_MAP_USER_STACK in the ASP bootloader of AMD processors may allow an attacker to send malformed syscalls, potentially leading to a denial of service and loss of integrity.

Affected Systems and Versions

Ryzen™ 2000 series Desktop Processors “Raven Ridge” AM4
Ryzen™ 2000 Series Desktop Processors “Pinnacle Ridge”
Ryzen™ 3000 Series Desktop Processors “Matisse” AM4
AMD Ryzen™ 5000 Series Desktop Processors “Vermeer” AM4
Ryzen™ 5000 Series Desktop processor with Radeon™ Graphics “Cezanne” AM4
2nd Gen AMD Ryzen™ Threadripper™ Processors “Colfax”
3rd Gen AMD Ryzen™ Threadripper™ Processors “Castle Peak” HEDT
Ryzen™ Threadripper™ PRO Processors “Castle Peak” WS
Athlon™ 3000 Series Mobile Processors with Radeon™ Graphics “Dali”/“Dali” ULP
Athlon™ 3000 Series Mobile Processors with Radeon™ Graphics “Pollock”
Ryzen™ 2000 Series Mobile Processors “Raven Ridge” FP5
Ryzen™ 3000 Series Mobile processor, 2nd Gen AMD Ryzen™ Mobile Processors with Radeon™ Graphics “Picasso”
Ryzen™ 3000 Series Mobile Processors with Radeon™ Graphics “Renoir”
Ryzen™ 5000 Series Mobile Processors with Radeon™ Graphics “Lucienne”
Ryzen™ 5000 Series Mobile processors with Radeon™ Graphics “Cezanne”
1st Gen AMD EPYC™ Processors
2nd Gen AMD EPYC™ Processors
3rd Gen AMD EPYC™ Processors

Exploitation Mechanism

The vulnerability can be exploited by an attacker utilizing a malicious Uapp or ABL to send malformed or invalid syscalls to the ASP bootloader, potentially resulting in a denial of service and integrity compromise.

Mitigation and Prevention

Immediate Steps to Take

Apply security patches provided by AMD promptly.
Monitor AMD's security bulletins for updates and advisories.

Long-Term Security Practices

Implement secure coding practices to prevent input validation vulnerabilities.
Conduct regular security assessments and audits of the processor environment.

Patching and Updates

It is crucial to update the affected processors with the latest patches and firmware updates provided by AMD.