SB2021081243 - Ubuntu update for openssh

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Main Vulnerability Database SB2021081243

SB2021081243 - Ubuntu update for openssh

Published: August 12, 2021 Updated: March 9, 2023

Security Bulletin ID SB2021081243
CSH Severity
Medium
Patch available
YES
Number of vulnerabilities 2
Exploitation vector Remote access
Highest impact Denial of service

Breakdown by Severity

Medium 50% Low 50%
  • Low
  • Medium
  • High
  • Critical

Description

This security bulletin contains information about 2 vulnerabilities.


1) Null pointer dereference (CVE-ID: CVE-2016-10708)

CWE-ID: CWE-476 - NULL Pointer Dereference

CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Clear


The vulnerability allows a remote attacker to cause DoS condition on the target system.

The vulnerability exists due to improper processing of out-of-sequence NEWKEYS messages, as defined in the kex.c and packet.c source code files. A remote attacker can send an out-of-sequence NEWKEYS message, trigger a NULL pointer dereference condition and cause the sshd daemon to crash.


2) User enumeration (CVE-ID: CVE-2018-15473)

CWE-ID: CWE-388 - Error Handling

CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:A/U:Green


The vulnerability allows a remote attacker to enumerate all accounts on the system.

The vulnerability exists due to a logical error in auth2-gss.c, auth2-hostbased.c, and auth2-pubkey.c files when processing authentication requests. A remote attacker can send a specially crafted chain of packets and monitor behavior of openssh server to determine presence of a valid username. The server will drop connection upon receiving a malformed authentication packets if the username is valid.


Remediation

Install update from vendor's website.

References