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Linux KernelOperating system · Linux

CVE-2023-6240

MEDIUM · 6.5 CVSS v3.1 Published 2024-02-04
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
74/100
Remediation priority · Elevated
Remotely reachable No privileges 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 Marvin vulnerability side-channel leakage was found in the RSA decryption operation in the Linux Kernel. This issue may allow a network attacker to decrypt ciphertexts or forge signatures, limiting the services that use that private key.

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 · moderate confidence

A Marvin vulnerability side-channel timing leakage exists in the Linux Kernel's RSA decryption implementation. By measuring timing differences during RSA operations, a network-attacker can infer information about the private key, potentially allowing decryption of ciphertexts or forging of signatures.

MitigationApply Linux kernel security updates that address the RSA timing side-channel. Ensure affected systems use RSA with proper padding (OAEP for encryption, PSS for signatures) and verify the patch eliminates measurable timing differences.

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:= 7.0= 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
Network
Complexity
High
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
Low
Availability
None

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

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. Check the running kernel version
    Run 'uname -r' or 'cat /proc/version' to identify the kernel version. Compare against any distribution-specific security advisories for CVE-2023-6240.
    Affected if The kernel version is older than the patched version provided by your distribution and RSA decryption is performed on the system.
  2. Identify RSA private key usage
    Search for RSA private keys or certificates on the system using 'find / -name "*.key" -o -name "*.pem"' or review application configurations for RSA key references.
    Affected if RSA private keys are present and used for decryption or signing operations.
  3. Verify RSA padding configuration in applications
    Review application configurations and code that perform RSA operations. Check whether OAEP padding is used for encryption/decryption and PSS padding for signatures. Look for 'RSA_PKCS1_PADDING' or 'RSA_NO_PADDING' in code or configs.
    Affected if Applications use RSA without OAEP (for encryption) or PSS (for signatures), relying on PKCS#1 v1.5 padding.
  4. Audit active network services using RSA
    Run 'netstat -tulpn' or 'ss -tulpn' to identify listening services. Review those performing authentication or decryption with RSA.
    Affected if Network-facing services perform RSA decryption or signature operations without proper padding.
  5. Check for timing-attack mitigations
    Review system documentation or contact application vendors to confirm whether timing-attack countermeasures (constant-time operations) are implemented in RSA code paths.
    Affected if The RSA implementation lacks constant-time operations and proper padding.

A system is affected if it runs a Linux kernel version prior to the CVE-2023-6240 fix and performs RSA decryption or signing operations using PKCS#1 v1.5 padding instead of OAEP/PSS, exposing timing differences to network attackers.

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.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Apply Linux kernel security updates that address the RSA timing side-channel. Ensure affected systems use RSA with proper padding (OAEP for encryption, PSS for signatures) and verify the patch eliminates measurable timing differences.

Fix this in Linux Kernel Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA3.0 h
21.0 hours of engineering $3,680
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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-2023-6240 in production — separate from our analysis above.

No notes yet

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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