CVE-2021-26377
📋 TL;DR
This vulnerability in AMD's Trusted OS (TOS) allows a malicious userspace process to trigger an integer overflow by exploiting insufficient parameter validation during process space allocation, potentially leading to a denial of service. It affects systems with AMD processors that use the vulnerable TOS, primarily impacting server and workstation environments where untrusted userspace processes could be present.
💻 Affected Systems
- AMD EPYC processors
- AMD Ryzen processors with Trusted OS
⚠️ Manual Verification Required
This CVE does not have specific version information in our database, so automatic vulnerability detection cannot determine if your system is affected.
Why? The CVE database entry doesn't specify which versions are vulnerable (no version ranges provided by the vendor/NVD).
🔒 Custom verification scripts are available for registered users. Sign up free to download automated test scripts.
- Review the CVE details at NVD
- Check vendor security advisories for your specific version
- Test if the vulnerability is exploitable in your environment
- Consider updating to the latest version as a precaution
⚠️ Risk & Real-World Impact
Worst Case
A successful exploit could crash the Trusted OS, causing system instability or denial of service, potentially disrupting critical operations on affected AMD-based systems.
Likely Case
In most scenarios, exploitation leads to a localized denial of service within the TOS, affecting only specific processes or services without compromising the entire system.
If Mitigated
With proper access controls and patching, the risk is minimal, as exploitation requires a malicious userspace process, which can be restricted through user privilege management.
🎯 Exploit Status
Exploitation requires local access and the ability to execute a malicious userspace process, making it moderately complex but feasible for attackers with sufficient privileges.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Refer to AMD advisories for specific firmware or software updates.
Vendor Advisory: https://www.amd.com/en/resources/product-security/bulletin/AMD-SB-4012.html
Restart Required: No
Instructions:
1. Check AMD advisories for affected products. 2. Apply the recommended firmware or software updates from AMD. 3. Verify the update by checking system logs or version information.
🔧 Temporary Workarounds
Restrict user privileges
allLimit local user access to reduce the risk of malicious userspace processes exploiting the vulnerability.
Use OS-specific tools like sudoers configuration or user group management.
🧯 If You Can't Patch
- Implement strict access controls to prevent untrusted users from running local processes.
- Monitor system logs for unusual process crashes or denial-of-service indicators.
🔍 How to Verify
Check if Vulnerable:
Check system firmware or software version against AMD advisories; use commands like 'dmidecode' on Linux or system information tools on Windows.Check Version:
On Linux: 'sudo dmidecode -t bios' or 'cat /proc/cpuinfo'; on Windows: 'wmic bios get smbiosbiosversion'Verify Fix Applied:
After applying updates, verify the version has changed and check for any related error logs or stability issues.📡 Detection & Monitoring
Log Indicators:
- Unexpected crashes or errors in Trusted OS logs
- System logs showing process termination related to TOS
Network Indicators:
- None, as this is a local vulnerability
SIEM Query:
Example: search for 'Trusted OS crash' or 'AMD TOS error' in system event logs.