---
id: CVE-2024-6409
title: >-
  A race condition vulnerability was discovered in how signals are handled by
  OpenSSH's server (sshd)
summary: >-
  A race condition vulnerability was discovered in how signals are handled by
  OpenSSH's server (sshd). If a remote attacker does not authenticate within a
  set time period, then sshd's SIGALRM handler is called asynchronously.
  However, this…
severity: high
cvss: 7
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H'
cwe:
  - CWE-364
published: '2024-07-08'
updated: '2026-08-21'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2024-6409'
references:
  - url: 'https://access.redhat.com/errata/RHSA-2024:4457'
    label: secalert@redhat.com
  - url: 'https://access.redhat.com/errata/RHSA-2024:4613'
    label: secalert@redhat.com
  - url: 'https://access.redhat.com/errata/RHSA-2024:4716'
    label: secalert@redhat.com
  - url: 'https://access.redhat.com/errata/RHSA-2024:4910'
    label: secalert@redhat.com
  - url: 'https://access.redhat.com/errata/RHSA-2024:4955'
    label: secalert@redhat.com
  - url: 'https://access.redhat.com/errata/RHSA-2024:4960'
    label: secalert@redhat.com
  - url: 'https://access.redhat.com/errata/RHSA-2024:5444'
    label: secalert@redhat.com
  - url: 'https://access.redhat.com/security/cve/CVE-2024-6409'
    label: secalert@redhat.com
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2295085'
    label: secalert@redhat.com
  - url: 'http://www.openwall.com/lists/oss-security/2024/07/08/2'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'http://www.openwall.com/lists/oss-security/2024/07/09/2'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'http://www.openwall.com/lists/oss-security/2024/07/09/5'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'http://www.openwall.com/lists/oss-security/2024/07/10/1'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'http://www.openwall.com/lists/oss-security/2024/07/10/2'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://access.redhat.com/errata/RHSA-2024:4457'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://access.redhat.com/errata/RHSA-2024:4613'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://access.redhat.com/errata/RHSA-2024:4716'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://access.redhat.com/security/cve/CVE-2024-6409'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://almalinux.org/blog/2024-07-09-cve-2024-6409/'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2295085'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://bugzilla.suse.com/show_bug.cgi?id=1227217'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://explore.alas.aws.amazon.com/CVE-2024-6409.html'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: >-
      https://github.com/openela-main/openssh/commit/c00da7741d42029e49047dd89e266d91dcfbffa0
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://security-tracker.debian.org/tracker/CVE-2024-6409'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://security.netapp.com/advisory/ntap-20240712-0003/'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://sig-security.rocky.page/issues/CVE-2024-6409/'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://ubuntu.com/security/CVE-2024-6409'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://www.suse.com/security/cve/CVE-2024-6409.html'
    label: af854a3a-2127-422b-91ae-364da2661108
tags:
  - nvd
epss: 0.27935
epssPercentile: 0.98016
ingestedAt: '2026-08-21T13:17:17.636Z'
---

## Overview

A race condition vulnerability was discovered in how signals are handled by OpenSSH's server (sshd). If a remote attacker does not authenticate within a set time period, then sshd's SIGALRM handler is called asynchronously. However, this signal handler calls various functions that are not async-signal-safe, for example, syslog(). As a consequence of a successful attack, in the worst case scenario, an attacker may be able to perform a remote code execution (RCE) as an unprivileged user running the sshd server.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.