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Ubuntu 20.04 LTS : libssh vulnerability (USN-5053-1)

medium Nessus Plugin ID 152869

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Synopsis

The remote Ubuntu host is missing a security update.

Description

The remote Ubuntu 20.04 LTS / 21.04 host has packages installed that are affected by a vulnerability as referenced in the USN-5053-1 advisory.

 - A flaw has been found in libssh in versions prior to 0.9.6. The SSH protocol keeps track of two shared secrets during the lifetime of the session. One of them is called secret_hash and the other session_id.
 Initially, both of them are the same, but after key re-exchange, previous session_id is kept and used as an input to new secret_hash. Historically, both of these buffers had shared length variable, which worked as long as these buffers were same. But the key re-exchange operation can also change the key exchange method, which can be based on hash of different size, eventually creating 'secret_hash' of different size than the session_id has. This becomes an issue when the session_id memory is zeroed or when it is used again during second key re-exchange. (CVE-2021-3634)

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

Solution

Update the affected packages.

See Also

https://ubuntu.com/security/notices/USN-5053-1

Plugin Details

Severity: Medium

ID: 152869

File Name: ubuntu_USN-5053-1.nasl

Version: 1.8

Type: local

Agent: unix

Published: 8/26/2021

Updated: 10/23/2023

Supported Sensors: Agentless Assessment, Frictionless Assessment Agent, Frictionless Assessment AWS, Frictionless Assessment Azure, Nessus Agent, Nessus

Risk Information

VPR

Risk Factor: Low

Score: 3.6

CVSS v2

Risk Factor: Medium

Base Score: 4

Temporal Score: 3

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

CVSS Score Source: CVE-2021-3634

CVSS v3

Risk Factor: Medium

Base Score: 6.5

Temporal Score: 5.7

Vector: CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Temporal Vector: CVSS:3.0/E:U/RL:O/RC:C

Vulnerability Information

CPE: cpe:/o:canonical:ubuntu_linux:20.04:-:lts, p-cpe:/a:canonical:ubuntu_linux:libssh-4, p-cpe:/a:canonical:ubuntu_linux:libssh-dev, p-cpe:/a:canonical:ubuntu_linux:libssh-gcrypt-4, p-cpe:/a:canonical:ubuntu_linux:libssh-gcrypt-dev

Required KB Items: Host/cpu, Host/Ubuntu, Host/Ubuntu/release, Host/Debian/dpkg-l

Exploit Ease: No known exploits are available

Patch Publication Date: 8/26/2021

Vulnerability Publication Date: 8/26/2021

Reference Information

CVE: CVE-2021-3634

IAVA: 2022-A-0041-S

USN: 5053-1