[ GLSA 201606-12 ] libssh and libssh2

[GLSA]

Gentoo Linux Security Advisory

Title: libssh and libssh2: Multiple vulnerabilities (GLSA 201606-12)
Severity: normal
Exploitable: remote
Date: June 26, 2016
Bug(s): #533366, #575474, #575484
ID: 201606-12

Synopsis

Multiple vulnerabilities have been found in libssh and libssh2, the
worst of which allows remote attackers to cause Denial of Service.


Background

libssh is a mulitplatform C library implementing the SSHv2 and SSHv1
protocol on client and server side.


Affected Packages

Package: net-libs/libssh
Vulnerable: < 0.7.3
Unaffected: >= 0.7.3
Architectures: All supported architectures

Package: net-libs/libssh2
Vulnerable: < 1.7.0
Unaffected: >= 1.7.0
Architectures: All supported architectures


Description

libssh and libssh2 both have a bits/bytes confusion bug and generate an
abnormaly short ephemeral secret for the diffie-hellman-group1 and
diffie-hellman-group14 key exchange methods. The resulting secret is 128
bits long, instead of the recommended sizes of 1024 and 2048 bits
respectively.
Additionally, a double free on dangling pointers in initial key exchange
packets within libssh could leave dangling pointers in the session crypto
structures. It is possible to send a malicious kexinit package to
eventually cause a server to do a double-free before this fix. This could
be used for a Denial of Service attack.


Impact

Remote attackers may gain access to confidential information due to the
short keysize generated by libssh and libssh2, or cause a Denial of
Service condition.


Workaround

There is no known workaround at this time.

Resolution

All libssh users should upgrade to the latest version: