CVE-2020-24513: Intel Atom C3308 Information Disclosure

CVE-2020-24513 Overview

CVE-2020-24513 is a domain-bypass transient execution vulnerability affecting multiple Intel Atom, Celeron, Pentium, and select Core processors. This hardware-level flaw allows an authenticated local user to potentially bypass security domain boundaries during speculative execution, enabling unauthorized information disclosure. The vulnerability is particularly concerning for environments where multiple security domains share physical processors, such as virtualized and cloud computing infrastructure.

Critical Impact

Authenticated attackers with local access can exploit transient execution to bypass domain isolation and leak sensitive information across security boundaries, potentially exposing cryptographic keys, credentials, and other confidential data from adjacent security domains.

Affected Products

• Intel Atom C3000 Series Processors (C3308, C3336, C3338, C3508, C3538, C3558, C3708, C3750, C3758, C3808, C3830, C3850, C3858, C3950, C3955, C3958)
• Intel Atom X5 and X6 Series Processors (X5-A3930, X5-A3940, X5-A3950, X5-A3960, X6200FE, X6211E, X6212RE, X6413E, X6425E, X6425RE, X6427FE)
• Intel Celeron J and N Series (J3355, J3455, J4005, J4025, J4105, J4125, J6413, N3350, N3450, N4000, N4020, N4100, N4120, N6211)
• Intel Pentium Silver Series (J5005, J5040, N5000, N5030) and Pentium J/N Series (J4205, J6425, N4200, N4200E, N6415)
• Intel Core i3-L13G4 and Core i5-L16G7 Processors
• Siemens SIMATIC Drive Controller, ET 200SP Open Controller, and IPC127E Firmware
• Debian Linux 9.0 and 10.0

Discovery Timeline

• June 9, 2021 - CVE-2020-24513 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2020-24513

Vulnerability Analysis

This vulnerability belongs to the class of transient execution side-channel attacks that exploit speculative execution optimizations in modern processors. The flaw specifically affects Intel Atom-based processors and allows authenticated users to bypass domain isolation mechanisms that are designed to prevent data leakage between different security contexts.

The vulnerability enables an attacker to potentially observe data that should be inaccessible across security domain boundaries. In multi-tenant environments such as cloud infrastructure or virtualized systems, this could allow a malicious virtual machine or process to infer sensitive data from co-located workloads belonging to different tenants or security domains.

Root Cause

The root cause lies in the microarchitectural implementation of transient (speculative) execution in affected Intel processors. During speculative execution, the processor may temporarily execute instructions and access data before confirming whether the execution path is correct. While incorrect speculative results are eventually discarded architecturally, they can leave observable traces in microarchitectural state elements such as caches.

In this specific vulnerability, the domain isolation mechanisms fail to properly prevent transient instructions from accessing data across security domain boundaries. This allows an attacker to construct side-channel primitives that can infer data values through timing measurements or other observable microarchitectural effects.

Attack Vector

The attack requires local access and authenticated user privileges on the target system. An attacker would typically deploy a malicious process or virtual machine on hardware that also hosts target workloads containing sensitive data. The attack process then executes carefully crafted instruction sequences designed to:

1. Trigger speculative execution that crosses security domain boundaries
2. Create observable microarchitectural side effects based on accessed data values
3. Measure these side effects through timing analysis or other techniques to reconstruct sensitive information

This vulnerability is primarily exploitable through local code execution, making systems with untrusted user access or multi-tenant virtualization particularly vulnerable. For detailed technical analysis, refer to the Intel Security Advisory SA-00465.

Detection Methods for CVE-2020-24513

Indicators of Compromise

• Unusual patterns of cache timing measurements or performance counter access from user-space processes
• Processes repeatedly accessing memory in patterns consistent with Flush+Reload or Prime+Probe side-channel techniques
• Anomalous CPU performance counter values indicating elevated speculative execution activity
• Applications attempting to use timing instructions (RDTSC, RDTSCP) at high frequency

Detection Strategies

• Monitor for processes making excessive use of high-precision timing instructions that are commonly used in side-channel attacks
• Implement hardware performance counter monitoring to detect unusual cache activity patterns
• Deploy processor microcode version tracking to ensure systems are running patched firmware
• Use SentinelOne's kernel-level visibility to detect anomalous process behaviors indicative of side-channel attack techniques

Monitoring Recommendations

• Maintain an accurate hardware inventory identifying all systems with affected Intel Atom, Celeron, Pentium, and Core processors
• Track BIOS/UEFI and microcode update status across the fleet to ensure timely patching
• Monitor virtualized environments for unusual cross-VM timing patterns that may indicate exploitation attempts
• Enable enhanced logging on Siemens industrial control systems using affected processors

How to Mitigate CVE-2020-24513

Immediate Actions Required

• Apply Intel microcode updates addressing CVE-2020-24513 from the Intel Security Advisory SA-00465
• Update BIOS/UEFI firmware to versions containing the patched microcode
• For Siemens industrial systems, apply firmware updates per the Siemens Security Advisory SSA-309571
• On Debian systems, apply kernel and microcode updates referenced in DSA-4934

Patch Information

Intel has released microcode updates that address this vulnerability. These updates are distributed through multiple channels:

• Intel Processor Microcode Updates: Available directly from Intel for integration into BIOS/UEFI firmware
• Operating System Updates: Linux distributions including Debian have released kernel and intel-microcode package updates
• Siemens Firmware Updates: Industrial control systems using affected processors require firmware updates from Siemens

For Debian Linux systems, apply updates as described in DSA-4934 and the Debian LTS Announcement.

Workarounds

• Restrict local access to affected systems to reduce the attack surface for authenticated users
• In virtualized environments, consider workload isolation by scheduling sensitive workloads on dedicated physical hosts
• Implement process sandboxing and resource quotas to limit the ability of potentially malicious processes to perform timing measurements
• Disable or restrict access to high-precision timing sources where feasible, though this may impact application functionality

# Check current microcode version on Linux systems
cat /proc/cpuinfo | grep -E "microcode|model name" | head -4

# Update intel-microcode package on Debian/Ubuntu
sudo apt update
sudo apt install intel-microcode

# Verify microcode update was applied (requires reboot)
dmesg | grep microcode