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FreeBSDOperating system

CVE-2024-7589

HIGH · 8.1 CVSS v3.1 Published 2024-08-12
Fix available
A fix is available. Upgrade to 13.0 / 13.3 or later.
See remediation →
90/100
Remediation priority · Urgent
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 signal handler in sshd(8) may call a logging function that is not async-signal-safe. The signal handler is invoked when a client does not authenticate within the LoginGraceTime seconds (120 by default). This signal handler executes in the context of the sshd(8)'s privileged code, which is not sandboxed and runs with full root privileges. This issue is another instance of the problem in CVE-2024-6387 addressed by FreeBSD-SA-24:04.openssh. The faulty code in this case is from the integration of blacklistd in OpenSSH in FreeBSD. As a result of calling functions that are not async-signal-safe in the privileged sshd(8) context, a race condition exists that a determined attacker may be able to exploit to allow an unauthenticated remote code execution as root.

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 signal handler in sshd calls a non-async-signal-safe logging function when clients fail to authenticate within the LoginGraceTime period (default 120 seconds). This signal handler executes in the privileged sshd context (not sandboxed, running as root), creating a race condition that can be exploited for unauthenticated remote code execution as root. This is a second instance (CVE-2024-6387) stemming from blacklistd integration in FreeBSD's OpenSSH.

MitigationApply the FreeBSD patch for this vulnerability or upgrade to a patched OpenSSH version. As a temporary hardening measure, reduce LoginGraceTime from the 120-second default to limit the attack window.

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
FreeBSDOperating system
Affected:< 13.0>= 13.1, < 13.3= 13.3= 14.0= 14.1

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
High
Availability
High

CVSS:3.1/AV:N/AC:H/PR:N/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 the operating system
    Run 'uname -a' or check /etc/os-release to confirm this is a FreeBSD system
    Affected if The system is not FreeBSD (this vulnerability only affects FreeBSD)
  2. Check the FreeBSD version
    Run 'freebsd-version -k' or 'uname -r' to get the kernel version
    Affected if The version is < 13.0, or between 13.1 and 13.3, or exactly 13.3, 14.0, or 14.1
  3. Verify sshd is running
    Run 'ps aux | grep sshd' or check if port 22 is listening with 'sockstat -4 -l | grep :22'
    Affected if sshd is not running (the vulnerability cannot be triggered)
  4. Check the LoginGraceTime setting
    Run 'grep -i logingracetime /etc/ssh/sshd_config' or use 'sshd -T' to see effective configuration (default is 120 seconds)
    Affected if LoginGraceTime is set to a non-zero value (the signal handler vulnerability only triggers when authentication times out)
  5. Confirm the signal handler behavior
    This is inherent to the code. If running an affected FreeBSD version with default/sshd config, the race condition exists. There is no simple config check; version-based detection is the primary method.
    Affected if Running an affected FreeBSD version with sshd enabled and LoginGraceTime > 0

A system is affected if it is FreeBSD versions 13.0, 13.1-13.3, 13.3, 14.0, or 14.1 with sshd running and LoginGraceTime set to a non-zero value (default 120 seconds), allowing the signal handler race condition to be triggered during failed authentication attempts.

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
Upgrade available Upgrade to 13.0 / 13.3 or later
Fixed in 13.013.3
Interim mitigation

Apply the FreeBSD patch for this vulnerability or upgrade to a patched OpenSSH version. As a temporary hardening measure, reduce LoginGraceTime from the 120-second default to limit the attack window.

Recommended fix Moderate confidence

FreeBSD 14.1 or later, or 13.3-STABLE after security patch application

  1. Check the current FreeBSD version with: uname -r
  2. Check for available FreeBSD security advisories at security.freebsd.org for the latest patches
  3. Apply the relevant FreeBSD security patch (FreeBSD-SA-24:XX.openssh or subsequent advisory addressing CVE-2024-7589)
  4. Alternatively, upgrade to a patched FreeBSD release (14.1 or later, or 13.3-STABLE after patch)
  5. After patching, restart the sshd service: service sshd restart
  6. Verify sshd is running correctly: service sshd status

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

Fix this in FreeBSD Scoped from the published advisory
  • Consultation3.0 h
  • Implementation4.0 h
  • Testing6.0 h
  • Review / QA3.0 h
16.0 hours of engineering $2,760
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Scan for this in your stack

Free · runs locally
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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-2024-7589 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