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CVE-2024-6409

Openssh: possible remote code execution due to a race condition in signal handling affecting red hat enterprise linux 9

7.0 HighFix available

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.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
High
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
Low
Integrity
Low
Availability
High

Exploit likelihood

27.9%Up 27.9 points since Jul 9, 2024
90%50%10%1%

What each source reports

CVE List Score used 7.0

Openssh: possible remote code execution due to a race condition in signal handling affecting red hat enterprise linux 9

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.

Record
CVE-2024-6409
CVSS 3.1
7.0 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H
Weakness
CWE-364
Updated
2026-11-06
EUVDEUVD-2024-47983 7.0

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.

Record
EUVD-2024-47983
CVSS 3.1
7.0 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H
Updated
2026-11-06
GitHub AdvisoriesGHSA-79hg-h6r6-64mm 7.0

A signal handler race condition vulnerability was found in OpenSSH's server (sshd), where a...

A signal handler race condition vulnerability was found in OpenSSH's server (sshd), where a client does not authenticate within LoginGraceTime seconds (120 by default, 600 in old OpenSSH versions), then sshd's SIGALRM handler is called asynchronously. However, this signal handler calls various functions that are not async-signal-safe, for example, syslog(). This issue leaves it vulnerable to a signal handler race condition on the cleanup_exit() function, which introduces the same vulnerability as CVE-2024-6387 in the unprivileged child of the SSHD server.

Record
GHSA-79hg-h6r6-64mm
CVSS 3.1
7.0 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H
Weakness
CWE-364
Updated
2026-11-02
NVD 7.0

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.

Record
CVE-2024-6409
CVSS 3.1
7.0 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H
Weakness
CWE-364
Updated
2026-11-07
OSVBELL-CVE-2024-6409 7.0

CVE-2024-6409 does not affect BellSoft software

Record
BELL-CVE-2024-6409
CVSS 3.1
7.0 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H
Updated
2026-11-02
OSV 7.0

Openssh: possible remote code execution due to a race condition in signal handling affecting red hat enterprise linux 9

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.

Record
CVE-2024-6409
CVSS 3.1
7.0 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H
Weakness
CWE-364
Updated
2026-11-07
Show 9 moreShow less
OSVOESA-2024-1870 7.0

openssh security update

OpenSSH is the premier connectivity tool for remote login with the SSH protocol. \ It encrypts all traffic to eliminate eavesdropping, connection hijacking, and \ other attacks. In addition, OpenSSH provides a large suite of secure tunneling \ capabilities, several authentication methods, and sophisticated configuration options.

Security Fix(es):

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.(CVE-2024-6409)

Record
OESA-2024-1870
CVSS 3.1
7.0 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H
Updated
2026-11-02
OSVOESA-2024-1871 7.0

openssh security update

OpenSSH is the premier connectivity tool for remote login with the SSH protocol. \ It encrypts all traffic to eliminate eavesdropping, connection hijacking, and \ other attacks. In addition, OpenSSH provides a large suite of secure tunneling \ capabilities, several authentication methods, and sophisticated configuration options.

Security Fix(es):

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.(CVE-2024-6409)

Record
OESA-2024-1871
CVSS 3.1
7.0 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H
Updated
2026-11-02
OSVOESA-2024-1872 7.0

openssh security update

OpenSSH is the premier connectivity tool for remote login with the SSH protocol. \ It encrypts all traffic to eliminate eavesdropping, connection hijacking, and \ other attacks. In addition, OpenSSH provides a large suite of secure tunneling \ capabilities, several authentication methods, and sophisticated configuration options.

Security Fix(es):

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.(CVE-2024-6409)

Record
OESA-2024-1872
CVSS 3.1
7.0 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H
Updated
2026-11-02
OSVRHSA-2024:4457 7.0

Red Hat Security Advisory: openssh security update

Record
RHSA-2024:4457
CVSS 3.1
7.0 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H
Updated
2026-11-02
OSVRHSA-2024:4716 7.0

Red Hat Security Advisory: openssh security update

Record
RHSA-2024:4716
CVSS 3.1
7.0 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H
Updated
2026-11-02
OSVRHSA-2024:4910 7.0

Red Hat Security Advisory: openssh security update

Record
RHSA-2024:4910
CVSS 3.1
7.0 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H
Updated
2026-11-02
OSVALSA-2024:4457 No score

Moderate: openssh security update

OpenSSH is an SSH protocol implementation supported by a number of Linux, UNIX, and similar operating systems. It includes the core files necessary for both the OpenSSH client and server.

Security Fix(es):

  • openssh: Possible remote code execution due to a race condition in signal handling affecting AlmaLinux(CVE-2024-6409)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

Record
ALSA-2024:4457
Updated
2026-11-02
OSVCLSA-2024-1721929402 No score

openssh: Fix of CVE-2024-6409

  • CVE-2024-6409: fix signal handler race condition vulnerability in sshd server
Record
CLSA-2024-1721929402
Updated
2026-11-02
OSVRLSA-2024:4457 No score

Moderate: openssh security update

OpenSSH is an SSH protocol implementation supported by a number of Linux, UNIX, and similar operating systems. It includes the core files necessary for both the OpenSSH client and server.

Security Fix(es):

  • openssh: Possible remote code execution due to a race condition in signal handling affecting Rocky Linux 9 (CVE-2024-6409)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

Record
RLSA-2024:4457
Updated
2026-11-02

Affected products

Show 2 moreShow less

Affected packages

Affected packages
PackageAffectedFixed
openssh
AlmaLinux:9
before 8.7p1-38.el9_4.4
8.7p1-38.el9_4.4
openssh-askpass
AlmaLinux:9
before 8.7p1-38.el9_4.4
8.7p1-38.el9_4.4
openssh-clients
AlmaLinux:9
before 8.7p1-38.el9_4.4
8.7p1-38.el9_4.4
openssh-keycat
AlmaLinux:9
before 8.7p1-38.el9_4.4
8.7p1-38.el9_4.4
openssh-server
AlmaLinux:9
before 8.7p1-38.el9_4.4
8.7p1-38.el9_4.4
pam_ssh_agent_auth
AlmaLinux:9
before 0.10.4-5.38.el9_4.4
0.10.4-5.38.el9_4.4
openssh
TuxCare:AlmaLinux:9.2
before 8.7p1-30.el9_2.tuxcare.els6
8.7p1-30.el9_2.tuxcare.els6
openssh-askpass
TuxCare:AlmaLinux:9.2
before 8.7p1-30.el9_2.tuxcare.els6
8.7p1-30.el9_2.tuxcare.els6
openssh-clients
TuxCare:AlmaLinux:9.2
before 8.7p1-30.el9_2.tuxcare.els6
8.7p1-30.el9_2.tuxcare.els6
openssh-keycat
TuxCare:AlmaLinux:9.2
before 8.7p1-30.el9_2.tuxcare.els6
8.7p1-30.el9_2.tuxcare.els6
Show 71 moreShow less
Affected packages
PackageAffectedFixed
openssh-server
TuxCare:AlmaLinux:9.2
before 8.7p1-30.el9_2.tuxcare.els6
8.7p1-30.el9_2.tuxcare.els6
openssh-sk-dummy
TuxCare:AlmaLinux:9.2
before 8.7p1-30.el9_2.tuxcare.els6
8.7p1-30.el9_2.tuxcare.els6
pam_ssh_agent_auth
TuxCare:AlmaLinux:9.2
before 0.10.4-5.30.el9_2.tuxcare.els6
0.10.4-5.30.el9_2.tuxcare.els6
openssh
openEuler:22.03-LTS-SP1
before 8.8p1-32.oe2203sp1
8.8p1-32.oe2203sp1
openssh
openEuler:22.03-LTS-SP3
before 8.8p1-32.oe2203sp3
8.8p1-32.oe2203sp3
openssh
openEuler:22.03-LTS-SP4
before 8.8p1-32.oe2203sp4
8.8p1-32.oe2203sp4
openssh-askpass
Red Hat:enterprise_linux:9::appstream
before 0:8.7p1-38.el9_4.4
0:8.7p1-38.el9_4.4
openssh-askpass-debuginfo
Red Hat:enterprise_linux:9::appstream
before 0:8.7p1-38.el9_4.4
0:8.7p1-38.el9_4.4
openssh-clients-debuginfo
Red Hat:enterprise_linux:9::appstream
before 0:8.7p1-38.el9_4.4
0:8.7p1-38.el9_4.4
openssh-debuginfo
Red Hat:enterprise_linux:9::appstream
before 0:8.7p1-38.el9_4.4
0:8.7p1-38.el9_4.4
openssh-debugsource
Red Hat:enterprise_linux:9::appstream
before 0:8.7p1-38.el9_4.4
0:8.7p1-38.el9_4.4
openssh-keycat-debuginfo
Red Hat:enterprise_linux:9::appstream
before 0:8.7p1-38.el9_4.4
0:8.7p1-38.el9_4.4
openssh-server-debuginfo
Red Hat:enterprise_linux:9::appstream
before 0:8.7p1-38.el9_4.4
0:8.7p1-38.el9_4.4
openssh-sk-dummy-debuginfo
Red Hat:enterprise_linux:9::appstream
before 0:8.7p1-38.el9_4.4
0:8.7p1-38.el9_4.4
pam_ssh_agent_auth
Red Hat:enterprise_linux:9::appstream
before 0:0.10.4-5.38.el9_4.4
0:0.10.4-5.38.el9_4.4
pam_ssh_agent_auth-debuginfo
Red Hat:enterprise_linux:9::appstream
before 0:0.10.4-5.38.el9_4.4
0:0.10.4-5.38.el9_4.4
openssh
Red Hat:enterprise_linux:9::baseos
before 0:8.7p1-38.el9_4.4
0:8.7p1-38.el9_4.4
openssh-askpass-debuginfo
Red Hat:enterprise_linux:9::baseos
before 0:8.7p1-38.el9_4.4
0:8.7p1-38.el9_4.4
openssh-clients
Red Hat:enterprise_linux:9::baseos
before 0:8.7p1-38.el9_4.4
0:8.7p1-38.el9_4.4
openssh-clients-debuginfo
Red Hat:enterprise_linux:9::baseos
before 0:8.7p1-38.el9_4.4
0:8.7p1-38.el9_4.4
openssh-debuginfo
Red Hat:enterprise_linux:9::baseos
before 0:8.7p1-38.el9_4.4
0:8.7p1-38.el9_4.4
openssh-debugsource
Red Hat:enterprise_linux:9::baseos
before 0:8.7p1-38.el9_4.4
0:8.7p1-38.el9_4.4
openssh-keycat
Red Hat:enterprise_linux:9::baseos
before 0:8.7p1-38.el9_4.4
0:8.7p1-38.el9_4.4
openssh-keycat-debuginfo
Red Hat:enterprise_linux:9::baseos
before 0:8.7p1-38.el9_4.4
0:8.7p1-38.el9_4.4
openssh-server
Red Hat:enterprise_linux:9::baseos
before 0:8.7p1-38.el9_4.4
0:8.7p1-38.el9_4.4
openssh-server-debuginfo
Red Hat:enterprise_linux:9::baseos
before 0:8.7p1-38.el9_4.4
0:8.7p1-38.el9_4.4
openssh-sk-dummy-debuginfo
Red Hat:enterprise_linux:9::baseos
before 0:8.7p1-38.el9_4.4
0:8.7p1-38.el9_4.4
pam_ssh_agent_auth-debuginfo
Red Hat:enterprise_linux:9::baseos
before 0:0.10.4-5.38.el9_4.4
0:0.10.4-5.38.el9_4.4
openssh-askpass
Red Hat:rhel_eus:9.2::appstream
before 0:8.7p1-30.el9_2.7
0:8.7p1-30.el9_2.7
openssh-askpass-debuginfo
Red Hat:rhel_eus:9.2::appstream
before 0:8.7p1-30.el9_2.7
0:8.7p1-30.el9_2.7
openssh-clients-debuginfo
Red Hat:rhel_eus:9.2::appstream
before 0:8.7p1-30.el9_2.7
0:8.7p1-30.el9_2.7
openssh-debuginfo
Red Hat:rhel_eus:9.2::appstream
before 0:8.7p1-30.el9_2.7
0:8.7p1-30.el9_2.7
openssh-debugsource
Red Hat:rhel_eus:9.2::appstream
before 0:8.7p1-30.el9_2.7
0:8.7p1-30.el9_2.7
openssh-keycat-debuginfo
Red Hat:rhel_eus:9.2::appstream
before 0:8.7p1-30.el9_2.7
0:8.7p1-30.el9_2.7
openssh-server-debuginfo
Red Hat:rhel_eus:9.2::appstream
before 0:8.7p1-30.el9_2.7
0:8.7p1-30.el9_2.7
openssh-sk-dummy-debuginfo
Red Hat:rhel_eus:9.2::appstream
before 0:8.7p1-30.el9_2.7
0:8.7p1-30.el9_2.7
pam_ssh_agent_auth
Red Hat:rhel_eus:9.2::appstream
before 0:0.10.4-5.30.el9_2.7
0:0.10.4-5.30.el9_2.7
pam_ssh_agent_auth-debuginfo
Red Hat:rhel_eus:9.2::appstream
before 0:0.10.4-5.30.el9_2.7
0:0.10.4-5.30.el9_2.7
openssh
Red Hat:rhel_eus:9.2::baseos
before 0:8.7p1-30.el9_2.7
0:8.7p1-30.el9_2.7
openssh-askpass-debuginfo
Red Hat:rhel_eus:9.2::baseos
before 0:8.7p1-30.el9_2.7
0:8.7p1-30.el9_2.7
openssh-clients
Red Hat:rhel_eus:9.2::baseos
before 0:8.7p1-30.el9_2.7
0:8.7p1-30.el9_2.7
openssh-clients-debuginfo
Red Hat:rhel_eus:9.2::baseos
before 0:8.7p1-30.el9_2.7
0:8.7p1-30.el9_2.7
openssh-debuginfo
Red Hat:rhel_eus:9.2::baseos
before 0:8.7p1-30.el9_2.7
0:8.7p1-30.el9_2.7
openssh-debugsource
Red Hat:rhel_eus:9.2::baseos
before 0:8.7p1-30.el9_2.7
0:8.7p1-30.el9_2.7
openssh-keycat
Red Hat:rhel_eus:9.2::baseos
before 0:8.7p1-30.el9_2.7
0:8.7p1-30.el9_2.7
openssh-keycat-debuginfo
Red Hat:rhel_eus:9.2::baseos
before 0:8.7p1-30.el9_2.7
0:8.7p1-30.el9_2.7
openssh-server
Red Hat:rhel_eus:9.2::baseos
before 0:8.7p1-30.el9_2.7
0:8.7p1-30.el9_2.7
openssh-server-debuginfo
Red Hat:rhel_eus:9.2::baseos
before 0:8.7p1-30.el9_2.7
0:8.7p1-30.el9_2.7
openssh-sk-dummy-debuginfo
Red Hat:rhel_eus:9.2::baseos
before 0:8.7p1-30.el9_2.7
0:8.7p1-30.el9_2.7
pam_ssh_agent_auth-debuginfo
Red Hat:rhel_eus:9.2::baseos
before 0:0.10.4-5.30.el9_2.7
0:0.10.4-5.30.el9_2.7
openssh-askpass
Red Hat:rhel_e4s:9.0::appstream
before 0:8.7p1-12.el9_0.3
0:8.7p1-12.el9_0.3
openssh-askpass-debuginfo
Red Hat:rhel_e4s:9.0::appstream
before 0:8.7p1-12.el9_0.3
0:8.7p1-12.el9_0.3
openssh-clients-debuginfo
Red Hat:rhel_e4s:9.0::appstream
before 0:8.7p1-12.el9_0.3
0:8.7p1-12.el9_0.3
openssh-debuginfo
Red Hat:rhel_e4s:9.0::appstream
before 0:8.7p1-12.el9_0.3
0:8.7p1-12.el9_0.3
openssh-debugsource
Red Hat:rhel_e4s:9.0::appstream
before 0:8.7p1-12.el9_0.3
0:8.7p1-12.el9_0.3
openssh-keycat-debuginfo
Red Hat:rhel_e4s:9.0::appstream
before 0:8.7p1-12.el9_0.3
0:8.7p1-12.el9_0.3
openssh-server-debuginfo
Red Hat:rhel_e4s:9.0::appstream
before 0:8.7p1-12.el9_0.3
0:8.7p1-12.el9_0.3
pam_ssh_agent_auth
Red Hat:rhel_e4s:9.0::appstream
before 0:0.10.4-4.12.el9_0.3
0:0.10.4-4.12.el9_0.3
pam_ssh_agent_auth-debuginfo
Red Hat:rhel_e4s:9.0::appstream
before 0:0.10.4-4.12.el9_0.3
0:0.10.4-4.12.el9_0.3
openssh
Red Hat:rhel_e4s:9.0::baseos
before 0:8.7p1-12.el9_0.3
0:8.7p1-12.el9_0.3
openssh-askpass-debuginfo
Red Hat:rhel_e4s:9.0::baseos
before 0:8.7p1-12.el9_0.3
0:8.7p1-12.el9_0.3
openssh-clients
Red Hat:rhel_e4s:9.0::baseos
before 0:8.7p1-12.el9_0.3
0:8.7p1-12.el9_0.3
openssh-clients-debuginfo
Red Hat:rhel_e4s:9.0::baseos
before 0:8.7p1-12.el9_0.3
0:8.7p1-12.el9_0.3
openssh-debuginfo
Red Hat:rhel_e4s:9.0::baseos
before 0:8.7p1-12.el9_0.3
0:8.7p1-12.el9_0.3
openssh-debugsource
Red Hat:rhel_e4s:9.0::baseos
before 0:8.7p1-12.el9_0.3
0:8.7p1-12.el9_0.3
openssh-keycat
Red Hat:rhel_e4s:9.0::baseos
before 0:8.7p1-12.el9_0.3
0:8.7p1-12.el9_0.3
openssh-keycat-debuginfo
Red Hat:rhel_e4s:9.0::baseos
before 0:8.7p1-12.el9_0.3
0:8.7p1-12.el9_0.3
openssh-server
Red Hat:rhel_e4s:9.0::baseos
before 0:8.7p1-12.el9_0.3
0:8.7p1-12.el9_0.3
openssh-server-debuginfo
Red Hat:rhel_e4s:9.0::baseos
before 0:8.7p1-12.el9_0.3
0:8.7p1-12.el9_0.3
pam_ssh_agent_auth-debuginfo
Red Hat:rhel_e4s:9.0::baseos
before 0:0.10.4-4.12.el9_0.3
0:0.10.4-4.12.el9_0.3
openssh
Rocky Linux:9
before 0:8.7p1-38.el9_4.4
0:8.7p1-38.el9_4.4

History

History
RecordedChangedSources
factsCVE List, EUVD
first indexedCVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2024-6409 is a high vulnerability (CVSS 7.0) in Red Hat Enterprise Linux 9, published July 8, 2024. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 27.9%, the 98th percentile. Fixed in openssh 8.7p1-38.el9_4.4.

References

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