CVE-2024-6387 is a high-severity (CVSS 8.1) CWE-364 vulnerability. 75 public exploit references exist, so weaponization risk is real. A fix is available — see the affected versions and patch details below.
Openssh: regresshion - race condition in ssh allows rce/dos
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- A successful exploit gives an attacker total control of the affected component, not partial access.
Exploitation and automatability from CISA’s SSVC triage for CVE-2024-6387.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2024-6387 by exploitation likelihood (EPSS) against impact (CVSS). In the shaded patch-first corner (EPSS 50%+, CVSS 7.0+).
Where this sits among everything scored
Of 394,803 CVEs with a current EPSS score, this one falls in the ≥ 90% band (highlighted). Counts from FIRST.org, log-scaled.
Description
A security regression (CVE-2006-5051) was discovered in OpenSSH's server (sshd). There is a race condition which can lead sshd to handle some signals in an unsafe manner. An unauthenticated, remote attacker may be able to trigger it by failing to authenticate within a set time period.
Affected Products
almalinuxalmalinuxamazon linuxamazonmacosappleeosaristaubuntu linuxcanonicaldebian linuxdebianResearch use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
OpenSSH server (sshd) 9.8p1 - Race Condition
by Milad karimi · Apr 22, 2025
Detection & mitigation playbook
VulnerabilityDetect
Identify every host running the affected component and compare the installed build against the fixed version below — for source-built or distro-packaged software the version string, not a lockfile, is the source of truth (`dpkg -l`, `rpm -q`, or the binary's own `--version`).
Fix
Upgrade the affected component to the fixed release for CVE-2024-6387, or apply your distribution's backported patch — distro builds are often patched at an older version number, so check your vendor's advisory rather than the upstream version alone.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
Red Hat rates the severity of this flaw as Important for both Red Hat Enterprise Linux (RHEL) and OpenShift Container Platform (OCP). The most significant risk is Remote Code Execution, however this outcome requires significant resources to exploit. If mitigations are put in place, the consequences of exploitation are…
The below process can protect against a Remote Code Execution attack by disabling the LoginGraceTime parameter on Red Hat Enterprise Linux 9. However, the sshd server is still vulnerable to a Denial of Service if an attacker exhausts all the connections. 1) As root user, open the /etc/ssh/sshd_config 2) Add or edit the parameter configuration: ~~~ LoginGraceTime 0 ~~~ 3) Save and close the file 4) Restart the sshd daemon: ~~~ systemctl restart sshd.service ~~~ Setting LoginGraceTime to 0 disables the SSHD server's ability to drop connections if authentication is not completed within the specified timeout. If this mitigation is implemented, it is highly recommended to use a tool like…Source: Red Hat security advisory for CVE-2024-6387 (CC BY 4.0)
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat Enterprise Linux 9 | openssh-0:8.7p1-38.el9_4.1 | RHSA-2024:4312 |
| Red Hat Enterprise Linux 9.0 Update Services for SAP Solutions | openssh-0:8.7p1-12.el9_0.1 | RHSA-2024:4389 |
| Red Hat Enterprise Linux 9.2 Extended Update Support | openssh-0:8.7p1-30.el9_2.4 | RHSA-2024:4340 |
| Red Hat OpenShift Container Platform 4.13 | openshift/ose-rhel-coreos-9:413.92.202407091321-0 | RHSA-2024:4484 |
| Red Hat OpenShift Container Platform 4.14 | openshift/ose-rhel-coreos-9:414.92.202407091253-0 | RHSA-2024:4479 |
| Red Hat OpenShift Container Platform 4.15 | openshift/ose-rhel-coreos-9:415.92.202407091355-0 | RHSA-2024:4474 |
| Red Hat OpenShift Container Platform 4.16 | openshift/ose-rhel-coreos-9:416.94.202407081958-0 | RHSA-2024:4469 |
Frequently Asked Questions
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