CVE-2019-3858.md

Possible zero-byte allocation leading to an out-of-bounds read

Project libssh2 Security Advisory, March 18 2019 - Permalink

VULNERABILITY

A server could send a specially crafted partial SFTP packet with a zero value for the payload length. This zero value would be used to then allocate memory resulting in a zero byte allocation and possible out of bounds read (CWE-130).

There are no known exploits of this flaw at this time.

INFO

The Common Vulnerabilities and Exposures (CVE) project has assigned the name CVE-2019-3858 to this issue.

AFFECTED VERSIONS

• Affected versions: versions 0.3 up to and including 1.8.0
• Not affected versions: libssh2 >= 1.8.1

THE SOLUTION

libssh2 1.8.1 ensures the length of the payload is not zero before allocing the memory buffer using the value.

A patch for this problem is available

RECOMMENDATIONS

We suggest you take one of the following actions immediately, in order of preference:

A - Upgrade to libssh2 1.8.1 or later

B - Apply the patch and rebuild libssh2

TIME LINE

It was first reported to the libssh2 project on Dec 3 2018 by Chris Coulson.

libssh2 1.8.1 was released on March 18 2019, coordinated with the publication of this advisory.

CREDITS

Reported by Chris Coulson of Canonical Ltd.