CVE-2023-20558

Q: What is the severity of CVE-2023-20558?

CVE-2023-20558 has a CVSS score of 8.8 (HIGH). This vulnerability in AMD's CPM OEM SMM (System Management Mode) firmware allows a privileged attacker to manipulate control flow and tamper with SMM handlers. This could lead to escalation of privileges from ring 0 (kernel) to ring -2 (SMM), giving attackers full system control. It affects systems with vulnerable AMD processors and firmware.

8.8 HIGH

📋 TL;DR

This vulnerability in AMD's CPM OEM SMM (System Management Mode) firmware allows a privileged attacker to manipulate control flow and tamper with SMM handlers. This could lead to escalation of privileges from ring 0 (kernel) to ring -2 (SMM), giving attackers full system control. It affects systems with vulnerable AMD processors and firmware.

💻 Affected Systems

Products:

AMD Ryzen processors with CPM firmware

Versions: Specific firmware versions not publicly detailed in advisory

Operating Systems: All operating systems running on affected hardware

Default Config Vulnerable: ⚠️ Yes

Notes: Requires local privileged access to exploit; affects systems with vulnerable AMD CPM firmware versions

📦 What is this software?

⚠️ Risk & Real-World Impact

🔴

Worst Case

Complete system compromise with persistent firmware-level backdoor installation, allowing attackers to bypass all security controls including secure boot and hypervisors.

🟠

Likely Case

Privileged attacker (local administrator or compromised kernel) gains SMM-level access to read/write protected memory, install persistent malware, or disable security features.

🟢

If Mitigated

Attack limited to kernel-level access without SMM escalation if proper firmware updates are applied and SMM protections are enabled.

🌐 Internet-Facing: LOW

🏢 Internal Only: HIGH

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ✅ No

Complexity: HIGH

Exploitation requires privileged local access and detailed knowledge of AMD firmware internals; no public exploits known

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Refer to AMD advisory for specific firmware versions

Vendor Advisory: https://www.amd.com/en/resources/product-security/bulletin/amd-sb-1027.html

Restart Required: Yes

Instructions:

1. Check system manufacturer's website for BIOS/UEFI firmware updates 2. Download appropriate firmware for your system model 3. Follow manufacturer's firmware update instructions carefully 4. Reboot system to apply update

🔧 Temporary Workarounds

Restrict local administrative access

all

Limit number of users with local administrative privileges to reduce attack surface

Enable SMM protection features

all

Enable SMM protection settings in BIOS/UEFI if available

🧯 If You Can't Patch

Implement strict access controls to limit local administrative privileges
Monitor for suspicious SMM-related activity and privilege escalation attempts

🔍 How to Verify

Check if Vulnerable:

Check BIOS/UEFI firmware version against AMD advisory; use manufacturer's system information tools

Check Version:

wmic bios get smbiosbiosversion (Windows) or dmidecode -t bios (Linux)

Verify Fix Applied:

Verify firmware version has been updated to patched version; check system logs for successful firmware update

📡 Detection & Monitoring

Log Indicators:

Unexpected firmware modification attempts
SMM handler access from non-SMM code
Privilege escalation attempts

Network Indicators:

None - this is a local privilege escalation vulnerability

SIEM Query:

Search for: firmware modification events, SMM access violations, or unexpected privilege changes

📊 Metadata

CVE ID: CVE-2023-20558

CVSS v3 Score: 8.8 (HIGH)

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CWE: CWE-670

Published: April 2, 2023

Last Updated: February 20, 2025

🔗 References

https://www.amd.com/en/resources/product-security/bulletin/amd-sb-1027.html Vendor Advisory
https://www.amd.com/en/resources/product-security/bulletin/amd-sb-1027.html Vendor Advisory

📋 TL;DR

💻 Affected Systems

📦 What is this software?

Athlon Gold 3150u Firmware by Amd

Athlon Silver 3050u Firmware by Amd

Ryzen 3 2200u Firmware by Amd

Ryzen 3 2300u Firmware by Amd

Ryzen 3 3200u Firmware by Amd

Ryzen 3 3250u Firmware by Amd

Ryzen 3 3300u Firmware by Amd

Ryzen 3 3300x Firmware by Amd

Ryzen 3 3350u Firmware by Amd

Ryzen 3 3450u Firmware by Amd

Ryzen 3 3500c Firmware by Amd

Ryzen 3 3500u Firmware by Amd

Ryzen 3 3550h Firmware by Amd

Ryzen 3 3580u Firmware by Amd

Ryzen 3 3700c Firmware by Amd

Ryzen 3 3700u Firmware by Amd

Ryzen 3 3750h Firmware by Amd

Ryzen 3 3780u Firmware by Amd

Ryzen 3 4300g Firmware by Amd

Ryzen 3 4300ge Firmware by Amd

Ryzen 3 5125c Firmware by Amd

Ryzen 3 5300g Firmware by Amd

Ryzen 3 5300ge Firmware by Amd

Ryzen 3 5400u Firmware by Amd

Ryzen 3 5425c Firmware by Amd

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Ryzen 5 2500u Firmware by Amd

Ryzen 5 2600 Firmware by Amd

Ryzen 5 2600h Firmware by Amd

Ryzen 5 2600x Firmware by Amd

Ryzen 5 2700 Firmware by Amd

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Ryzen 5 3500 Firmware by Amd

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Ryzen 5 4600g Firmware by Amd

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Ryzen 5 5560u Firmware by Amd

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Ryzen 5 5600h Firmware by Amd

Ryzen 5 5600hs Firmware by Amd

Ryzen 5 5600u Firmware by Amd

Ryzen 5 5625c Firmware by Amd

Ryzen 5 5625u Firmware by Amd

Ryzen 7 2700 Firmware by Amd

Ryzen 7 2700u Firmware by Amd

Ryzen 7 2700x Firmware by Amd

Ryzen 7 2800h Firmware by Amd

Ryzen 7 3700x Firmware by Amd

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Ryzen 7 3800xt Firmware by Amd

Ryzen 7 4700g Firmware by Amd

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Ryzen 7 5700g Firmware by Amd

Ryzen 7 5700ge Firmware by Amd

Ryzen 7 5800h Firmware by Amd

Ryzen 7 5800hs Firmware by Amd

Ryzen 7 5800u Firmware by Amd

Ryzen 7 5825c Firmware by Amd

Ryzen 7 5825u Firmware by Amd

Ryzen 9 3900 Firmware by Amd

Ryzen 9 3900x Firmware by Amd

Ryzen 9 3900xt Firmware by Amd

Ryzen 9 3950x Firmware by Amd

Ryzen 9 5900hs Firmware by Amd

Ryzen 9 5900hx Firmware by Amd

Ryzen 9 5980hs Firmware by Amd

Ryzen 9 5980hx Firmware by Amd

Ryzen 9 Pro 3900 Firmware by Amd

Ryzen Threadripper 2920x Firmware by Amd

Ryzen Threadripper 2950x Firmware by Amd

Ryzen Threadripper 2970wx Firmware by Amd

Ryzen Threadripper 2990wx Firmware by Amd

Ryzen Threadripper 3960x Firmware by Amd