CVE-2023-3640

Kernel-address disclosure via prefetch timing channel

Published Jul 24, 2023 · Updated Jul 21, 2026

Covert timing channel in the x86 Linux kernel on Red Hat Enterprise Linux 8 and 9 allows local users to disclose kernel addresses. The cpu_entry_area mapping remains visible to user space, so prefetchnta and prefetcht2 timing probes can locate its insufficiently randomized per-CPU offset. Exploitation requires local low-privileged access on a susceptible x86 CPU with KASLR and KPTI; the disclosure can weaken kernel defenses and support privilege escalation.

CVSS severity7.0
High
EPSS probability0.76%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Covert timing channel in the x86 Linux kernel on Red Hat Enterprise Linux 8 and 9 allows local users to disclose kernel addresses. The cpu_entry_area mapping remains visible to user space, so prefetchnta and prefetcht2 timing probes can locate its insufficiently randomized per-CPU offset. Exploitation requires local low-privileged access on a susceptible x86 CPU with KASLR and KPTI; the disclosure can weaken kernel defenses and support privilege escalation.

The record

CVE
CVE-2023-3640
Published
Jul 24, 2023
Updated
Jul 21, 2026
Vendor
Red Hat
Product
Red Hat Enterprise Linux 8
Classifications
CWE-203, CWE-385, T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Jul 24, 2023CVE publishedPublication date reported by the CVE source.
  2. Jul 21, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected versions are unavailable in this record. Check the vendor advisory for version and patch details.

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Red Hat · Red Hat Enterprise Linux 8Affected versions are unavailable in this record.
Red Hat · Red Hat Enterprise Linux 9Affected versions are unavailable in this record.

Published CVSS scores

7.0Red Hat, Inc.CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
7.8NIST National Vulnerability DatabaseCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-203Observable Discrepancy
CWE-385Covert Timing Channel
T1068Exploitation for Privilege Escalation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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