Scientific Linux Security Update : libssh2 on SL7.x x86_64

Medium Nessus Plugin ID 87561


The remote Scientific Linux host is missing one or more security updates.


A flaw was found in the way the kex_agree_methods() function of libssh2 performed a key exchange when negotiating a new SSH session. A man-in-the- middle attacker could use a crafted SSH_MSG_KEXINIT packet to crash a connecting libssh2 client. (CVE-2015-1782)

This update also fixes the following bugs :

- Previously, libssh2 did not correctly adjust the size of the receive window while reading from an SSH channel.
This caused downloads over the secure copy (SCP) protocol to consume an excessive amount of memory. A series of upstream patches has been applied on the libssh2 source code to improve handling of the receive window size. Now, SCP downloads work as expected.

- Prior to this update, libssh2 did not properly initialize an internal variable holding the SSH agent file descriptor, which caused the agent destructor to close the standard input file descriptor by mistake. An upstream patch has been applied on libssh2 sources to properly initialize the internal variable. Now, libssh2 closes only the file descriptors it owns.

After installing these updated packages, all running applications using libssh2 must be restarted for this update to take effect.


Update the affected packages.

See Also

Plugin Details

Severity: Medium

ID: 87561

File Name: sl_20151119_libssh2_on_SL7_x.nasl

Version: $Revision: 2.1 $

Type: local

Agent: unix

Published: 2015/12/22

Modified: 2015/12/22

Dependencies: 12634

Risk Information

Risk Factor: Medium


Base Score: 6.8

Vector: CVSS2#AV:N/AC:M/Au:N/C:P/I:P/A:P

Vulnerability Information

CPE: x-cpe:/o:fermilab:scientific_linux

Required KB Items: Host/local_checks_enabled, Host/cpu, Host/RedHat/release, Host/RedHat/rpm-list

Patch Publication Date: 2015/11/19

Reference Information

CVE: CVE-2015-1782