libssh2 SSH_MSG_CHANNEL_REQUEST Packet Handling Out-of-Bounds Read Vulnerability [CVE-2019-3862]

CVE Number – CVE-2019-3862

A vulnerability in libssh2 could allow an unauthenticated, remote attacker to access sensitive information or cause a denial of service (DoS) condition on a targeted system.The vulnerability is due to the improper parsing of SSH_MSG_CHANNEL_REQUEST packets that contain an exit status message, but no payload, by the affected software. An attacker could exploit this vulnerability by sending a crafted SSH_MSG_CHANNEL_REQUEST packet to the targeted system. A successful exploit could result in an out-of-bounds read condition, allowing the attacker to access sensitive information or cause a DoS condition.libssh2 confirmed the vulnerability and released software updates. 


  • To exploit this vulnerability, the attacker must send a crafted SSH_MSG_CHANNEL_REQUEST packet to the targeted system, making exploitation more difficult in environments that restrict network access from untrusted sources.


  • Administrators are advised to apply the appropriate updates.Administrators are advised to allow only trusted users to have network access.Administrators are advised to run both firewall and antivirus applications to minimize the potential of inbound and outbound threats.Administrators may consider using IP-based access control lists (ACLs) to allow only trusted systems to access the affected systems.Administrators can help protect affected systems from external attacks by using a solid firewall strategy.Administrators are advised to monitor affected systems.

Vendor Announcements

  • libssh2 has released a security advisory at the following link: CVE-2019-3862

Fixed Software

  • libssh2 has released software updates at the following link: libssh2 1.8.1

Duncan Newell

Duncan is a technology professional with over 20 years experience of working in various IT roles. He has a interest in cyber security, and has a wide range of other skills in radio, electronics and telecommunications.

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