Cisco Security Advisory
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On July 1, 2024, the Qualys Threat Research Unit (TRU) disclosed an unauthenticated, remote code execution vulnerability that affects the OpenSSH server (sshd) in glibc-based Linux systems.
CVE-2024-6387: A signal handler race condition was found in sshd, where a client does not authenticate within LoginGraceTime seconds (120 by default, 600 in old OpenSSH versions), then the sshd SIGALRM handler is called asynchronously. However, this signal handler calls various functions that are not async-signal-safe, for example, syslog().
For a description of this vulnerability, see the Qualys Security Advisory.
This advisory will be updated as additional information becomes available.
This advisory is available at the following link:
https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-openssh-rce-2024
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Cisco is investigating its product line to determine which products and cloud services may be affected by this vulnerability. Currently, no products are known to be affected. As the investigation progresses, Cisco will update this advisory with information about affected products and services.
The Vulnerable Products section will include Cisco bug IDs for each affected product or service. The bugs are accessible through the Cisco Bug Search Tool and contain additional platform-specific information, including workarounds (if available) and fixed software releases.
Vulnerable Products
Cisco is investigating its product line to determine which products may be affected by this vulnerability. Currently, no products are known to be affected. This section will be updated as information is available.
Products Confirmed Not Vulnerable
Cisco is investigating its product line to determine which products may be affected by this vulnerability. This section will be updated as information becomes available.
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Cisco recommends restricting SSH access to only trusted hosts. For the steps to apply infrastructure access control lists (ACLs) to prevent access to SSH services, see the following guides:
Cisco Guide to Harden Cisco IOS Devices - Limit Access to the Network with Infrastructure ACLs
Cisco Guide to Securing NX-OS Software Devices - Limiting Access to the Network with Infrastructure ACLs
Cisco UCS Hardening Guide - Limit Network Access with ACLs on Routers and Firewalls
Cisco Firewall Best Practices - Securing the Management Plane
Cisco Firepower Threat Defense Hardening GuideFor additional hardening documentation, see Tactical Resources.
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Any workarounds will be documented in the product-specific Cisco bugs, which are identified in the Vulnerable Products section of this advisory.
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For information about fixed software releases, consult the Cisco bugs identified in the Vulnerable Products section of this advisory.
When considering software upgrades, customers are advised to regularly consult the advisories for Cisco products, which are available from the Cisco Security Advisories page, to determine exposure and a complete upgrade solution.
In all cases, customers should ensure that the devices to be upgraded contain sufficient memory and confirm that current hardware and software configurations will continue to be supported properly by the new release. If the information is not clear, customers are advised to contact the Cisco Technical Assistance Center (TAC) or their contracted maintenance providers.
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The Cisco Product Security Incident Response Team (PSIRT) is aware that proof-of-concept exploit code is available for the vulnerability that is described in this advisory. However, customization is required for exploitation.
The Cisco PSIRT is not aware of any malicious use of the vulnerability that is described in this advisory.
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This vulnerability was publicly disclosed by the Qualys Threat Research Unit on July 1, 2024.
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To learn about Cisco security vulnerability disclosure policies and publications, see the Security Vulnerability Policy. This document also contains instructions for obtaining fixed software and receiving security vulnerability information from Cisco.
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Show LessVersion Description Section Status Date 1.0 Initial public release. — Interim 2024-JUL-02
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