Cisco warns of RCE regression affecting multiple products

Cisco has released a security advisory about a critical remote code execution (RCE) vulnerability, dubbed “regreSSHion,” that affects multiple products.

The vulnerability, tracked as CVE-2024-6387, was disclosed by the Qualys Threat Research Unit on July 1, 2024. This vulnerability affects the OpenSSH (sshd) server on glibc-based Linux systems and could allow unauthenticated attackers to gain root access on affected systems.

Vulnerability details

The regreSSHion vulnerability is a regression of an older bug (CVE-2006-5051) that was reintroduced in OpenSSH version 8.5p1, released in October 2020.

Join our free webinar to learn more about Combating slow DDoS attacksa major threat today.

The flaw involves a race condition in the sshd’s SIGALRM handler, which calls functions that are not async signal-safe, such as syslog().

An attacker could exploit this by opening multiple connections and not authenticating within the LoginGraceTime period, causing the vulnerable signal handler to be activated asynchronously.

Cisco has determined that multiple products across multiple categories are affected by this vulnerability.

The company is actively investigating its product line to determine the full scope of affected devices. The following table lists the affected products and their respective Cisco Bug IDs:

product category product name Cisco Bug ID Availability of fixed release
Network and content security devices Adaptive Security Devices (ASA) Software CSCwk61618
Firepower Management Center (FMC) software CSCwk61618
Firepower Threat Defense (FTD) software CSCwk61618
FXOS Firepower Chassis Manager CSCwk62297
Identity Services Engine (ISE) CSCwk61938
Secure Network Analysis CSCwk62315
Network management and provisioning Crosswork Data Gateway CSCwk62311 7.0.0 (August 2024)
Cybervision CSCwk62289
DNA space connector CSCwk62273
Prime infrastructure CSCwk62276
Smart on-site software manager CSCwk62288
Virtualized Infrastructure Manager CSCwk62277
Routing and Switching – Enterprise and Service Provider ASR 5000 Series Routers CSCwk62248
Nexus 3000 Series Switches CSCwk61235
Nexus 9000 Series Switches in Standalone NX-OS Mode CSCwk61235
Unified Computing Intersight Virtual Appliance CSCwk63145
Voice and Unified Communications Devices Emergency responder CSCwk63694
Unified Communications Manager CSCwk62318
Unified Communications Manager IM & Presence Service CSCwk63634
Unit connection CSCwk63494
Video, streaming, telepresence and transcoding devices Cisco Meeting Server CSCwk62286 SMU – CMS 3.9.2 (August 2024)

Mitigation and recommendations

Cisco recommends several steps to reduce the risk of exploitation:

  • Restrict SSH access: Restrict SSH access to only trusted hosts. This can be accomplished by applying infrastructure access control lists (ACLs) to prevent unauthorized access to SSH services.
  • Upgrading OpenSSH: Upgrade to the latest patched version of OpenSSH (9.8p1) once it is available in the package repositories of Linux distributions.
  • Customize LoginGraceTime: Set the LoginGraceTime parameter to 0 in the sshd configuration file to avoid the race condition, although this may lead to denial-of-service if all connection slots become occupied[1][6][7].

The Cisco Product Security Incident Response Team (PSIRT) is aware that proof-of-concept exploit code exists for this vulnerability. However, exploitation requires customization and there have been no reports of malicious use.

Cisco continues to evaluate all products and services for impact and will update this advisory as new information becomes available.

The regreSSHion vulnerability poses a significant risk to a wide range of Cisco products.

Customers are urged to follow Cisco’s recommendations and apply the necessary patches and mitigations to protect their systems from potential exploits.

"Is Your System Under Attack? Try Cynet XDR: Automated Detection & Response for Endpoints, Networks, & Users!"- Free Demo

Leave a Comment