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Linux KernelOperating system · Linux

CVE-2023-3640

HIGH · 7.8 CVSS v3.1 Published 2023-07-24
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
80/100
Remediation priority · High
Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
A possible unauthorized memory access flaw was found in the Linux kernel's cpu_entry_area mapping of X86 CPU data to memory, where a user may guess the location of exception stacks or other important data. Based on the previous CVE-2023-0597, the 'Randomize per-cpu entry area' feature was implemented in /arch/x86/mm/cpu_entry_area.c, which works through the init_cea_offsets() function when KASLR is enabled. However, despite this feature, there is still a risk of per-cpu entry area leaks. This issue could allow a local user to gain access to some important data with memory in an expected location and potentially escalate their privileges on the system.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

A flaw in the Linux kernel's x86 cpu_entry_area randomization allows local users to predict the location of exception stacks and other critical per-CPU data structures. Despite the CVE-2023-0597 fix adding randomize per-cpu entry area functionality via init_cea_offsets() when KASLR is enabled, the randomization can still be leaked, enabling a local attacker to access sensitive kernel memory locations and potentially escalate privileges.

MitigationApply the upstream kernel patch for CVE-2023-3640 which strengthens the cpu_entry_area randomization logic in arch/x86/mm/cpu_entry_area.c to prevent address leakage.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Linux KernelOperating system
Affected:all versions
Enterprise LinuxOperating system
Affected:= 8.0= 9.0

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify system architecture
    Run 'uname -m' or check /proc/cpuinfo to confirm the system is x86_64 or i686. This vulnerability only affects x86 architectures.
    Affected if System is not x86 (the vulnerability is specific to x86 cpu_entry_area)
  2. Confirm Linux kernel version
    Run 'uname -r' to get the running kernel version, then compare against the fixed version for your distribution.
    Affected if Kernel version is older than the version that includes the CVE-2023-3640 patch (check your distribution's security advisories)
  3. Check for cpu_entry_area implementation
    Inspect /arch/x86/mm/cpu_entry_area.c in the kernel source or module. Look for the init_cea_offsets() function and verify if randomization of exception stack locations is present.
    Affected if The cpu_entry_area mapping does not randomize exception stack locations, allowing address disclosure
  4. Verify stack address disclosure possibility
    As a local user, attempt to read kernel memory addresses via /proc/kallsyms, /proc/modules, or other interfaces that may expose per-CPU exception stack addresses. Compare addresses across reboots to check for randomization.
    Affected if Exception stack addresses are static or predictable across reboots, indicating insufficient randomization

A system is affected if it runs a Linux kernel on x86 architecture where the cpu_entry_area does not properly randomize exception stack locations, allowing local users to determine sensitive per-CPU memory addresses.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Apply the upstream kernel patch for CVE-2023-3640 which strengthens the cpu_entry_area randomization logic in arch/x86/mm/cpu_entry_area.c to prevent address leakage.

Recommended fix Moderate confidence

Red Hat Enterprise Linux 8.x: kernel-4.18.0-xxx or later (check RHSA advisory); RHEL 9.x: kernel-5.14.0-xxx or later (check RHSA advisory). For mainline Linux: kernel 6.4 or later contains the complete fix.

  1. Update the kernel package to the latest version available in Red Hat Enterprise Linux 8 or 9 repositories using: 'dnf update kernel' or 'yum update kernel'
  2. Reboot the system to load the updated kernel
  3. Verify the new kernel version is running using: 'uname -r'
  4. Confirm the cpu_entry_area randomization is properly enabled by checking kernel config options CONFIG_RANDOMIZE_BASE and relevant cpu_entry_area settings if built as modules
Caveat Kernel updates may require system reboot and could have compatibility implications with third-party kernel modules. Ensure backup and test in non-production environment first.

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Linux Kernel Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA4.0 h
22.0 hours of engineering $3,860
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2023-3640 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data