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Full vulnerability report · 2024
CVE-2024-6409High confidence

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

Unknown · Unknown

Official source article: Red Hat RHSA-2024:4457 ↗. Check the applicable product and release in the original source.

7.0HighCVSS 3.1
Recommended action
Patch only the product branches with a verified fix

High technical severity; prioritise exposed affected systems while verifying vendor guidance. Verified remediation exists for at least one product or source, but 5 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.

Fix availability varies by product
R
Operational reassessment

Published severity in operational context

Open reassessment dashboard →
Published severityHighOperational priority:Critical, raised one band.upgradedsince 5 Oct 2026

Evidence used

  • No CISA KEV confirmation is currently recorded.
  • The selected CVSS metric records a network-reachable, unauthenticated path with no user interaction.
  • EPSS is 27.93% for the current model date.

Compensating controls

  • Validate the affected product branch and deploy the verified fixed release.
  • Restrict the affected network interface to trusted sources where business-safe.
  • Monitor vendor guidance and exploitation sources for a material change.

Verification

  1. Confirm that the asset runs Unknown Unknown and falls inside the recorded affected range.
  2. Verify the installed build against the product-specific fixed version after deployment.
  3. Validate exposure, authentication requirements and compensating controls in the actual environment.
  4. Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Mitigation target: Within 3 daysRemediation target: Within 90 days

This automated reassessment organises public evidence. It does not know asset exposure, business impact or control effectiveness and does not replace CVSS or a human risk decision.

Cross-source reconciliation

Remediation availability differs by product scope

Verified remediation exists for at least one product or source, but 5 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.

Distribution package intelligence

Release-specific package status

Debian findings are scoped to the named distribution, release and source package. An absent finding does not mean a package is unaffected.

4 package states
Repository candidate not checked

A published vendor fix does not prove that a matching update is enabled and installable on a particular asset. Confirm the local package candidate before scheduling remediation.

Distribution releaseSource packageVendor stateFixed versionEvidence
Debian trixietrixie · sourceopensshNot affectedDebian marks this release not affected (fixed-version marker 0).Not published in this feedDebian Security Tracker ↗Source updated 6 Oct 2026
Debian bookwormbookworm · sourceopensshNot affectedDebian marks this release not affected (fixed-version marker 0).Not published in this feedDebian Security Tracker ↗Source updated 6 Oct 2026
Debian forkyforky · sourceopensshNot affectedDebian marks this release not affected (fixed-version marker 0).Not published in this feedDebian Security Tracker ↗Source updated 6 Oct 2026
Debian sidsid · sourceopensshNot affectedDebian marks this release not affected (fixed-version marker 0).Not published in this feedDebian Security Tracker ↗Source updated 6 Oct 2026
Direct vendor intelligence

Authoritative vendor CSAF and VEX advisories

Structured product status and remediation from the issuing vendor. Product-state explanations are always visible; large lists can be searched or downloaded.

2 current
CVE-2024-6409 · CSAF 2.0 · revision 3 · finalRed Hat Product Securityopenssh: Possible remote code execution due to a race condition in signal handling affecting Red Hat Enterprise Linux 9
275 fixed

The vendor explicitly identifies these products or versions as containing the fix.

  • rhcos@sha256:1e88ab770689bc27cb1966ff6aebc986997fe489dfb0243ccfe8010825629f2e_aarch64 as a component of Red Hat OpenShift Container Platform 4.13
  • rhcos@sha256:1e88ab770689bc27cb1966ff6aebc986997fe489dfb0243ccfe8010825629f2e_ppc64le as a component of Red Hat OpenShift Container Platform 4.13
  • rhcos@sha256:1e88ab770689bc27cb1966ff6aebc986997fe489dfb0243ccfe8010825629f2e_s390x as a component of Red Hat OpenShift Container Platform 4.13
  • rhcos@sha256:1e88ab770689bc27cb1966ff6aebc986997fe489dfb0243ccfe8010825629f2e_x86_64 as a component of Red Hat OpenShift Container Platform 4.13
  • rhcos@sha256:42f39b4a4d51b867e78be998522bd13b7344717dc72edd5f6f4cea42143d9d78_aarch64 as a component of Red Hat OpenShift Container Platform 4.14
  • rhcos@sha256:42f39b4a4d51b867e78be998522bd13b7344717dc72edd5f6f4cea42143d9d78_ppc64le as a component of Red Hat OpenShift Container Platform 4.14
  • rhcos@sha256:42f39b4a4d51b867e78be998522bd13b7344717dc72edd5f6f4cea42143d9d78_s390x as a component of Red Hat OpenShift Container Platform 4.14
  • rhcos@sha256:42f39b4a4d51b867e78be998522bd13b7344717dc72edd5f6f4cea42143d9d78_x86_64 as a component of Red Hat OpenShift Container Platform 4.14
  • rhcos@sha256:f45f6d1596c25672f1e6b4f8993be724c57298f2f2503c4e3429a906e540b69b_aarch64 as a component of Red Hat OpenShift Container Platform 4.15
  • rhcos@sha256:f45f6d1596c25672f1e6b4f8993be724c57298f2f2503c4e3429a906e540b69b_ppc64le as a component of Red Hat OpenShift Container Platform 4.15
  • rhcos@sha256:f45f6d1596c25672f1e6b4f8993be724c57298f2f2503c4e3429a906e540b69b_s390x as a component of Red Hat OpenShift Container Platform 4.15
  • rhcos@sha256:f45f6d1596c25672f1e6b4f8993be724c57298f2f2503c4e3429a906e540b69b_x86_64 as a component of Red Hat OpenShift Container Platform 4.15
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 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
For OpenShift Container Platform 4.13 see the following documentation, which will be updated shortly for this release, for important instructions on how to upgrade your cluster and fully apply this asynchronous errata update: https://docs.openshift.com/container-platform/4.13/release_notes/ocp-4-13-release-notes.html You may download the oc tool and use it to inspect release image metadata for x86_64, s390x, ppc64le, and aarch64 architectures. The image digests may be found at https://quay.io/repository/openshift-release-dev/ocp-release?tab=tags. The sha values for the release are (For x86_64 architecture) The image digest is sha256:7235b8e139da4ba4c17c2b4b9864c05c93c5f55f7c2f561e7f9796c7e6589917 (For s390x architecture) The image digest is sha256:04865553b69831321134ca4e61be8ad02548ccfd41a2941c09bf357d5120dbde (For ppc64le architecture) The image digest is sha256:471fc8ffaa8d14e5aff88b91dcf378291aec41ab524aa88a1562f4767bf57b62 (For aarch64 architecture) The image digest is sha256:83ddfc54da02ab4f523d181c7e9eeb24b3deef3bf6da3052e6db894f246c7a99 All OpenShift Container Platform 4.13 users are advised to upgrade to these updated packages and images when they are available in the appropriate release channel. To check for available updates, use the OpenShift CLI (oc) or web console. Instructions for upgrading a cluster are available at https://docs.openshift.com/container-platform/4.13/updating/updating-cluster-cli.html
SSA-398330 · CSAF 2.0 · revision 18 · interimSiemens ProductCERTSSA-398330: Vulnerabilities in the additional GNU/Linux subsystem of the SIMATIC S7-1500 CPU 1518(F)-4 PN/DP MFP >= V3.1.0 and < V3.1.5
5 known affected

The vendor explicitly identifies these products as affected by this CVE.

  • SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0)
  • SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0)
  • SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0)
  • SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0)
  • SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0)
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 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
Update to V3.1.5 or later version
Optional official sources

National CERT insights
?CERT means Computer Emergency Response Team; CSIRT is the closely related term Computer Security Incident Response Team.

Choose official national sources for this report. Each advisory shows its original language. Your selection is remembered on this device and included in shared links.

Official European source

ENISA European Vulnerability Database

Official EUVD identifiers, advisory evidence and known-exploited context. Missing fields are not treated as evidence of low risk.

1 current
ENISA EUVD identifier

EUVD-2024-47983

No EUVD known-exploited evidence

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.

EUVD state
Present in the current official mapping
Known exploitation
Not present in the current ENISA EUVD known-exploited dataset. This is not proof of no exploitation.
ENISA score
7.0 · CVSS 3.1
Advisory evidence
No linked advisory details stored yet
Recommended actionPatch only the product branches with a verified fix

High technical severity; prioritise exposed affected systems while verifying vendor guidance. Verified remediation exists for at least one product or source, but 5 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.

Fix availability varies by product
01

What, why and how

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.

What

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.

Why

The product uses a signal handler that introduces a race condition.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may execute code or commands in the affected security context.

What

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.

Why

The product uses a signal handler that introduces a race condition.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may execute code or commands in the affected security context.

02

Exploit reality and attack path

CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.

Observed exploitation
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
No confirmed evidence

No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.

Public PoC / exploit material
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
None recorded

No exploit-tagged reference or CISA SSVC proof-of-concept state is currently recorded. Research may still exist outside the structured feeds.

Likely attack path
a network path → Signal Handler Race Condition → execute code or commands in the affected security context
Attack surface
Network
Privileges required
None: unauthenticated exploitation is possible
User interaction
None
Attack complexity
High: exploitation depends on specific conditions
Security boundary
Unchanged: impact remains within the vulnerable component's security authority
Weakness
?CWE means Common Weakness Enumeration: a standard category for the underlying weakness.
CWE-364 ↗

CWE-364: Signal Handler Race Condition. The product uses a signal handler that introduces a race condition.

CVSS vector
?CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H

Common Vulnerability Scoring System 3.1: the compact vector below is decoded into plain language.

AVNetworkAttack vector: The vulnerable component can be reached over a network.ACHighAttack complexity: Successful exploitation depends on specific conditions outside the attacker's direct control.PRNonePrivileges required: The attacker does not need an account or existing privileges.UINoneUser interaction: No action by another user is required.SUnchangedScope: The security impact remains within the vulnerable component's authority.CLowConfidentiality impact: A successful attack can cause a limited loss.ILowIntegrity impact: A successful attack can cause a limited loss.AHighAvailability impact: A successful attack can cause a major loss.
Post-exploitation / living off the land
After compromise, an attacker may use built-in shells, scripting engines, scheduled tasks and native network utilities for discovery, persistence or movement. This is a plausible LoTL path, not evidence that it has occurred for every attack.
NetworkUnauthenticatedRemote code executionCWE-364
A

Official authority intelligence

Only matched European and national findings are included. Language selectors and unavailable sources are omitted.

ENISA EUVD · EUVD-2024-47983Official EUVD mapping

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.

Official EUVD record ↗
BSI · German · WID-SEC-2024-1913Red Hat OpenShift Container Platform: Mehrere Schwachstellen

Ein entfernter anonymer oder lokaler Angreifer kann mehrere Schwachstellen in Red Hat OpenShift Container Platform ausnutzen, um seine Privilegien zu erhöhen, beliebigen Code auszuführen, einen Denial-of-Service-Zustand zu erzeugen, vertrauliche Informationen offenzulegen, Dateien und Daten zu manipulieren oder Sicherheitsmaßnahmen zu umgehen.

Official advisory ↗
BSI · German · WID-SEC-2024-1547OpenSSH auf Red Hat Enterprise Linux 9: Schwachstelle ermöglicht Denial of Service

Ein entfernter, anonymer Angreifer kann eine Schwachstelle in OpenSSH auf Red Hat Enterprise Linux 9 ausnutzen, um einen Denial of Service Angriff durchzuführen.

Official advisory ↗
Cyber Security Agency of Singapore · English · CSA-SB-20240710Security Bulletin 10 Jul 2024

The Cyber Security Agency of Singapore included this CVE in its official Security Bulletin 10 Jul 2024, published on 10 July 2024. Open the linked bulletin for the product, severity and reference information published in that issue.

Official advisory ↗
CERT-FR · French · CERTFR-2025-AVI-0855Multiples vulnérabilités dans les produits Juniper Networks

VERecord?id=CVE-2024-4603 Référence CVE CVE-2024-47538 https://www.cve.org/CVERecord?id=CVE-2024-47538 Référence CVE CVE-2024-47607 https://www.cve.org/CVERecord?id=CVE-2024-47607 Référence CVE CVE-2024-47615 https://www.cve.org/CVERecord?id=CVE-2024-47615 Référence CVE CVE-2024-49761 https://www.cve.org/CVERecord?id=CVE-2024-49761 Référence CVE CVE-2024-52337 https://www.cve.org/CVERecord?id=CVE-2024-52337 Référence CVE CVE-2024-5564 https://www.cve.org/CVERecord?id=CVE-2024-5564 Référence CVE CVE-2024-5742 https://www.cve.org/CVERecord?id=CVE-2024-5742 Référence CVE CVE-2024-6126 https://www.cve.org/CVERecord?id=CVE-2024-6126 Référence CVE CVE-2024-6409 https://www.cve.org/CVERecord?id=CVE-2024-6409 Référence CVE CVE-2024-6655 https://www.cve.org/CVERecord?id=CVE-2024-6655 Référence CVE CVE-2024-8235 https://www.cve.org/CVERecord?id=CVE-2024-8235 Référence CVE CVE-2024-8508 https://www.cve.org/CVERecord?id=CVE-2024-8508 Référence CVE CVE-2024-9632 https://www.cve.org/CVERecord?id=CVE-2024-9632 Référence CVE CVE-2025-0624 https://www.cve.org/CVERecord?id=CVE-2025-0624 Référence CVE CVE-2025-11198 https://www.cve.org/CVERecord?id=CVE-2025-11198 Référence CVE CVE-2025-26594 https://www.cve.org/CVERecord?id=CVE-2025-26594 Référence CVE CVE-2025-26595 https://www.cve.org/CVERecord?id=CVE-2025-26

Official advisory ↗
CERT-FR · French · CERTFR-2024-AVI-0551Vulnérabilité OpenSSH dans des systèmes d'exploitation

Une vulnérabilité a été découverte dans OpenSSH. Elle permet à un attaquant de provoquer une exécution de code arbitraire à distance.

Official advisory ↗
KISA KrCERT/CC · Korean · KNVD-6238OpenSSH 제품 보안 업데이트 권고

Red Hat Enterprise Linux 9의 OpenSSH에서 발생하는 레이스 컨디션 취약점으로 인한 원격 코드 실행 취약점(CVE-2024-6409) [2][3]

Official advisory ↗
03

Patch and workaround

Operational remediation based on structured source evidence.

Status
?Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change.
Fix availability varies by product
Affected
Fixed
Action
Use the product-specific evidence above. Patch only products with a verified fixed release, and keep every affected or under-investigation state without a matching fix in the remediation queue.
Workaround
No verified workaround is recorded. If business-safe, reduce exposure to the affected interface and allow only trusted sources until authoritative guidance is available.
04

Evidence and provenance

Published 8 Jul 2024 · Last source change 21 Aug 2026, 12:24 UTC · CWE-364 · Signal Handler Race Condition

CVE recordCVE.org · 5.2
CVSS sourceCNA
EPSS source
?The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.
FIRST · tracked since 2026-08-14
European sourceENISA EUVD · EUVD-2024-47983
Product sourceUnavailable
Remediation sourceVendor CSAF · Red Hat Product Security
CWE sourceCNA
NVD statusNVD not scheduled

Missing structured fields: affected product, affected versions. Missing data is not evidence of low risk; review the primary advisory.

Material change intelligence

What changed after publication

View recent updates ↗

No material field changes have been recorded since change tracking began. Routine source refreshes and cosmetic edits are intentionally excluded.

Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
Fixed release or patch reference recorded
ENISA EUVD · EUVD-2024-47983↗Vendor CSAF · Red Hat Product Security↗CVE authority or vendor reference · Red Hat RHSA-2024:4457↗Official CVE record (CNA and ADP data)↗NVD record↗
Technical terms and abbreviations used in this report
CVE
Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
CVSS
Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
EPSS
Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
CWE
Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
CNA
CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
CISA ADP
Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
NVD
National Vulnerability Database: NIST's enrichment service for CVE records.
CERT / CSIRT
A computer security incident response team that publishes warnings or coordinates incident response.
PoC
Proof of concept: public material that demonstrates or helps reproduce exploitation.
CSAF
Common Security Advisory Framework: a machine-readable format for security advisories.
LoTL
Living off the land: abuse of legitimate tools or system functions during an attack.
Free version - for non-commercial use only.CVE-2024-6409 · cve.blacktree.nl