Intel Atom: Information disclosure via shared microarchitectural predictor state in Intel Atom processors (CVE-2024-43420) #shorts

Summary

Today we’re discussing CVE-2024-43420, a transient-execution side-channel vulnerability in Intel Atom processors. Published May 13, 2025, this flaw can expose sensitive data when an authenticated local user exploits shared microarchitectural predictor state. SUSE and Intel have issued microcode updates to mitigate the risk.

Product details

Affected products: Intel Atom® processors (see Intel’s references for exact model list). Vendor: Intel. SUSE has released updated microcode_ctl and ucode-intel packages that include fixes for CVE-2024-43420 (alongside CVE-2024-28956). Updates are available via standard SUSE repositories.

Vulnerability type summary

This is an Information Disclosure vulnerability caused by Shared Microarchitectural Predictor State that Influences Transient Execution. In short, it’s a side-channel exploit in the CPU’s branch predictor, similar to Spectre-class issues, allowing data leakage across privilege boundaries when properly triggered.

Details of the vulnerability

On vulnerable Intel Atom models, the CPU’s branch‐prediction structures can be trained by a local, authenticated user. By executing crafted code sequences, an attacker can manipulate the predictor state and infer bits of data from other processes or the OS kernel through timing differences. Unlike remote exploits, this requires code execution on the target box, but no special privileges beyond standard user access. Intel’s microcode patch closes the predictor‐state leakage channel; SUSE packages the updated firmware in microcode_ctl and ucode-intel.

Conclusion

If you run Intel Atom processors, treat CVE-2024-43420 seriously even though it’s a local attack. Apply the latest Intel microcode or install SUSE’s updated microcode_ctl/ucode-intel packages immediately. Regularly update firmware, monitor vendor advisories, and follow best practices for limiting untrusted code execution on servers and endpoints.

Watch the full video on YouTube: CVE-2024-43420

Remediation and exploitation details

This chain involves the following actors

  • Local authenticated user: attacker
  • System administrator: defender

This following systems are involved

  • Intel Atom processor (executes application code and maintains microarchitectural predictor state): vulnerable hardware
  • Host operating system (schedules processes and mediates access to hardware): execution environment

Attack entry point

  • Shared branch predictor state: the microarchitectural structure that records past branch outcomes and influences speculation across contexts

Remediation actions

System administrator
Apply Intel microcode update that isolates predictor state across contexts
Intel Atom processor
System administrator
Install SUSE microcode_ctl package fixes
Host operating system

Exploitation actions

log in to the machine or exploit a local application bug

Local authenticated user
Gain code execution in user space
Host operating system
Examples:
  • use valid credentials to open a shell
  • launch a local process with standard user privileges

execute a tight loop of indirect branches to train predictor history entries

Local authenticated user
Prime the branch predictor with a chosen pattern
Intel Atom processor
Examples:
  • repeat a sequence of jumps to target addresses A→B→A→B

sleep or wait for another process to run on the same core

Local authenticated user
Yield the CPU to victim context
Host operating system
Examples:
  • call sched_yield() or pause execution for a short interval

perform an operation in another process that causes the predictor to influence speculative paths

Local authenticated user
Trigger victim code that uses the same predictor entries
Intel Atom processor
Examples:
  • execute a branch in victim process that maps to the trained pattern

flush or evict branch target buffer entries then invoke the mispredicted branch

Local authenticated user
Force a misprediction and transient execution
Intel Atom processor
Examples:
  • use cache flush instructions or memory thrashing to clear predictor entry

use high-resolution timers to detect cache state changes after speculative execution

Local authenticated user
Measure side-channel effects to recover secret data
Intel Atom processor
Examples:
  • perform a cache-timing probe (for example, reload timing) on memory addresses touched during speculation

Related Content

NOTE: The following related content has not been vetted and may be unsafe.

CVE database technical details

CVE ID
CVE-2024-43420
Description
Exposure of sensitive information caused by shared microarchitectural predictor state that influences transient execution for some Intel Atom(R) processors may allow an authenticated user to potentially enable information disclosure via local access.
Provider
intel
CWE / problem types
Information Disclosure,Exposure of Sensitive Information caused by Shared Microarchitectural Predictor State that Influences Transient Execution
Affected Software Versions
n/a:Intel Atom(R) processors:[{'version': 'See references', 'status': 'affected'}]
Date Published
2025-05-13T21:03:09.384Z
Last Updated
2025-05-14T14:01:31.886Z