SB2016072705 - Fedora 23 update for openssh, selinux-policy

Description

This security bulletin contains information about 1 security vulnerability.

1) User enumeration via covert timing channel (CVE-ID: CVE-2016-6210)

The vulnerability allows a remote attacker to enumerate users on system.

The vulnerability exists in most systems where the Blowfish algorithm runs faster than SHA256/SHA512. A remote unauthenticated attacker can determine valid usernames by sending a specially crafted request with a large password (approximately 10,000 characters) to the target ssh daemon. On systems where a valid user's password has been hashed with SHA256/SHA512, the response time will be shorter for a non-existent username than for a valid username.

Successful exploitation of this vulnerability may result in disclosure or user logins.

Remediation

Install update from vendor's website.

References

• https://bodhi.fedoraproject.org/updates/FEDORA-2016-9402100276