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FedoraOperating system · Fedoraproject

CVE-2023-51767

HIGH · 7.0 CVSS v3.1 Published 2023-12-24
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
72/100
Remediation priority · Elevated
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
OpenSSH through 10.0, when common types of DRAM are used, might allow row hammer attacks (for authentication bypass) because the integer value of authenticated in mm_answer_authpassword does not resist flips of a single bit. NOTE: this is applicable to a certain threat model of attacker-victim co-location in which the attacker has user privileges. NOTE: this is disputed by the Supplier, who states "we do not consider it to be the application's responsibility to defend against platform architectural weaknesses."

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

OpenSSH through 10.0 contains a vulnerability in mm_answer_authpassword where the authenticated integer variable can be flipped by a single bit via row hammer attacks on certain non-ECC DRAM modules. An attacker with user-level privileges on a co-located system can flip bits in the SSH authentication state, potentially bypassing password authentication by flipping the authenticated flag.

MitigationThis is a hardware-level vulnerability requiring platform architectural changes - not a software patch. Mitigations include deploying ECC DRAM, upgrading to row-hammer-resistant memory modules, or implementing physical isolation between multi-tenant systems.

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
FedoraOperating system
Affected:= 39
Enterprise LinuxOperating system
Affected:= 8.0= 9.0
OpensshApplication
Affected:all versions

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
High
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:H/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. Check installed OpenSSH version
    Run 'sshd -V' or 'rpm -q openssh-server' (RHEL/Fedora) or 'pkg_info -I openssh' (OpenBSD) to determine the version
    Affected if Version is 10.0 or earlier (OpenSSH through 10.0)
  2. Verify if password authentication is enabled
    Inspect /etc/ssh/sshd_config and look for 'PasswordAuthentication yes' or check if 'PasswordAuthentication no' is commented out
    Affected if PasswordAuthentication is set to 'yes' or is not explicitly set to 'no' (password auth is enabled)
  3. Confirm SSH service is running
    Run 'systemctl status sshd' (RHEL/Fedora) or check process list for sshd
    Affected if SSH daemon is active and accepting connections (vulnerability only applies to running SSH service)
  4. Check for multi-tenant environment exposure
    Review system placement: determine if the system is hosted in a shared/colocated environment where untrusted users have local user-level access
    Affected if System is co-located with untrusted tenant systems or allows shared physical access to non-privileged users
  5. Identify memory module type
    Run 'dmidecode -t memory' and examine the 'Type' or 'Memory Device Type' fields for ECC or non-ECC designation
    Affected if Memory modules are non-ECC DDR (the vulnerability targets specific non-ECC DRAM modules susceptible to row hammer)

A system is affected if it runs OpenSSH 10.0 or earlier, has password authentication enabled, uses non-ECC DRAM, and exists in a co-located environment where an attacker could perform row hammer attacks from a neighboring virtual machine or container.

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

This is a hardware-level vulnerability requiring platform architectural changes - not a software patch. Mitigations include deploying ECC DRAM, upgrading to row-hammer-resistant memory modules, or implementing physical isolation between multi-tenant systems.

Fix this in Fedora Scoped from the published advisory
  • Consultation8.0 h
  • Implementation40.0 h
  • Testing16.0 h
  • Review / QA8.0 h
72.0 hours of engineering $12,640
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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-2023-51767 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
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