CVE-2020-24513: Intel Atom C3308 Information Disclosure

CVE-2020-24513 Overview

CVE-2020-24513 is a domain-bypass transient execution vulnerability affecting a wide range of Intel Atom, Celeron, Pentium, and select Core processors. An authenticated local user can exploit speculative execution behavior to read data across security domains. The flaw enables information disclosure but does not affect integrity or availability. Intel disclosed the issue in advisory INTEL-SA-00465, and downstream vendors including Debian and Siemens issued coordinated updates for affected Linux distributions and industrial control systems built on impacted silicon.

Critical Impact
A locally authenticated attacker can leak sensitive data across security boundaries through speculative side-channel behavior on dozens of Intel Atom-class processors used in servers, embedded systems, and industrial controllers.

Affected Products

Intel Atom C-series, P-series, and X-series processors (including C3308, C3758, P5942B, x6425E)
Intel Celeron and Pentium Silver families (including J4125, N4120, Pentium Silver J5040) plus Intel Core i3-L13G4 and i5-L16G7
Debian Linux 9 and 10; Siemens SIMATIC Drive Controller, ET 200SP Open Controller, and IPC127E firmware

Discovery Timeline

2021-06-09 - CVE-2020-24513 published to NVD alongside Intel advisory INTEL-SA-00465
2021-07-22 - Debian LTS publishes microcode update announcement
2024-11-21 - Last updated in NVD database

Technical Details for CVE-2020-24513

Vulnerability Analysis

The vulnerability is a domain-bypass transient execution flaw, a class of side-channel weakness related to Microarchitectural Data Sampling (MDS) and Special Register Buffer Data Sampling (SRBDS). Speculative execution within affected Atom-class cores can transiently access data that should be isolated by privilege or security domain boundaries. An attacker measures microarchitectural state — typically cache timing — to reconstruct values leaked during the speculative window. The CWE is recorded as NVD-CWE-noinfo because the disclosure references the architectural class rather than a specific software weakness.

Root Cause

The root cause lies in how affected Intel processors fill internal buffers during speculative execution. Data from one security domain remains accessible to transient instructions executing in another domain before the processor retires or squashes the speculative path. Because the leak occurs in silicon, the fix requires updated CPU microcode and operating system or hypervisor coordination, not application-level patching.

Attack Vector

Exploitation requires local authenticated access (AV:L, PR:L) and no user interaction. The attacker runs code on the same physical core as a victim workload — for example, a co-located process, a sibling VM, or a container — and triggers speculative loads followed by a covert-channel readout. The scope is changed (S:C), meaning the attacker can extract information belonging to a different security domain such as kernel memory, another VM, or an SGX enclave. There is no public proof-of-concept tied to this specific CVE, and it is not listed in the CISA KEV catalog.

No verified public exploit code exists for CVE-2020-24513. Refer to the Intel Security Advisory SA-00465 for the architectural description.

Detection Methods for CVE-2020-24513

Indicators of Compromise

No file-based or network IOCs exist; transient execution attacks leave no on-disk artifacts
Unexpected long-running CPU-bound processes performing repeated, tight-loop memory access patterns on shared cores
Workloads measuring high-resolution timers (rdtsc, clock_gettime) at unusually high frequency from unprivileged processes

Detection Strategies

Inventory all hosts and embedded devices running affected Intel Atom, Celeron, Pentium, and Core SKUs and verify the installed CPU microcode revision
Detect installation of unsigned or out-of-band microcode loaders and monitor dmesg for microcode: updated messages outside change windows
Hunt for unprivileged processes that pin themselves to specific cores using sched_setaffinity while continuously probing cache lines

Monitoring Recommendations

Ingest microcode version telemetry from Linux (/proc/cpuinfo) and Windows (HKLM\HARDWARE\DESCRIPTION\System\CentralProcessor) into a central data store and alert on drift
Track Siemens SIMATIC firmware versions against Siemens Security Advisory SSA-309571
Correlate Debian package update events for intel-microcode against the Debian Security Advisory DSA-4934

How to Mitigate CVE-2020-24513

Immediate Actions Required

Apply the Intel microcode update referenced in Intel Security Advisory SA-00465 to all affected processors
Update Debian 9 and Debian 10 hosts using the intel-microcode package from DSA-4934 and the Debian LTS announcement
Upgrade Siemens SIMATIC Drive Controller, ET 200SP Open Controller, and IPC127E firmware per SSA-309571
Restrict local code execution on multi-tenant hosts and audit accounts that hold shell or container runtime access

Patch Information

Intel released updated CPU microcode addressing the domain-bypass transient execution behavior. Debian shipped fixed intel-microcode packages for Debian 9 (LTS) and Debian 10. Siemens released firmware updates for SIMATIC industrial PCs and controllers that embed the affected silicon. Operating system vendors load microcode early in boot, so a reboot is required after applying the package update.

Workarounds

Disable simultaneous multithreading (SMT) on affected cores where co-tenancy across security domains is a concern
Avoid co-locating untrusted workloads with sensitive workloads on the same physical CPU until microcode is applied
Where microcode cannot be deployed (legacy embedded devices), enforce strict allow-listing of executable code and remove interactive local access

bash

# Verify Intel microcode is loaded and current on Debian/Linux hosts
sudo apt-get update && sudo apt-get install --only-upgrade intel-microcode
grep 'microcode' /proc/cpuinfo | head -1
dmesg | grep -i microcode
# Reboot to ensure the updated microcode is applied early in boot
sudo systemctl reboot