Amazon Linux 2 : dnsmasq (ALAS-2021-1587)

low Nessus Plugin ID 145454

Language:

Synopsis

The remote Amazon Linux 2 host is missing a security update.

Description

The version of dnsmasq installed on the remote host is prior to 2.76-16. It is, therefore, affected by multiple vulnerabilities as referenced in the ALAS2-2021-1587 advisory.

A flaw was found in dnsmasq. When getting a reply from a forwarded query, dnsmasq checks in the forward.c:reply_query() if the reply destination address/port is used by the pending forwarded queries.
However, it does not use the address/port to retrieve the exact forwarded query, substantially reducing the number of attempts an attacker on the network would have to perform to forge a reply and get it accepted by dnsmasq. This issue contrasts with RFC5452, which specifies a query's attributes that all must be used to match a reply. This flaw allows an attacker to perform a DNS Cache Poisoning attack. If chained withCVE-2020-25685orCVE-2020-25686, the attack complexity of a successful attack is reduced. The highest threat from this vulnerability is to data integrity. (CVE-2020-25684)

A flaw was found in dnsmasq. When getting a reply from a forwarded query, dnsmasq checks in forward.c:reply_query(), which is the forwarded query that matches the reply, by only using a weak hash of the query name. Due to the weak hash (CRC32 when dnsmasq is compiled without DNSSEC, SHA-1 when it is) this flaw allows an off-path attacker to find several different domains all having the same hash, substantially reducing the number of attempts they would have to perform to forge a reply and get it accepted by dnsmasq. This is in contrast with RFC5452, which specifies that the query name is one of the attributes of a query that must be used to match a reply. This flaw could be abused to perform a DNS Cache Poisoning attack. If chained withCVE-2020-25684the attack complexity of a successful attack is reduced.
The highest threat from this vulnerability is to data integrity. (CVE-2020-25685)

A flaw was found in dnsmasq. When receiving a query, dnsmasq does not check for an existing pending request for the same name and forwards a new request. By default, a maximum of 150 pending queries can be sent to upstream servers, so there can be at most 150 queries for the same name. This flaw allows an off- path attacker on the network to substantially reduce the number of attempts that it would have to perform to forge a reply and have it accepted by dnsmasq. This issue is mentioned in the Birthday Attacks section of RFC5452. If chained withCVE-2020-25684, the attack complexity of a successful attack is reduced. The highest threat from this vulnerability is to data integrity. (CVE-2020-25686)

Tenable has extracted the preceding description block directly from the tested product security advisory.

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

Solution

Run 'yum update dnsmasq' to update your system.

Plugin Details

Severity: Low

ID: 145454

File Name: al2_ALAS-2021-1587.nasl

Version: 1.4

Type: local

Agent: unix

Family: Amazon Linux Local Security Checks

Published: 1/26/2021

Updated: 12/11/2024

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

Risk Information

VPR

Risk Factor: Low

Score: 2.2

CVSS v2

Risk Factor: Medium

Base Score: 4.3

Temporal Score: 3.2

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

CVSS Score Source: CVE-2020-25686

CVSS v3

Risk Factor: Low

Base Score: 3.7

Temporal Score: 3.2

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

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

Vulnerability Information

CPE: p-cpe:/a:amazon:linux:dnsmasq, cpe:/o:amazon:linux:2, p-cpe:/a:amazon:linux:dnsmasq-debuginfo, p-cpe:/a:amazon:linux:dnsmasq-utils

Required KB Items: Host/local_checks_enabled, Host/AmazonLinux/release, Host/AmazonLinux/rpm-list

Exploit Ease: No known exploits are available

Patch Publication Date: 1/25/2021

Vulnerability Publication Date: 1/19/2021

Reference Information

CVE: CVE-2020-25684, CVE-2020-25685, CVE-2020-25686

ALAS: 2021-1587

Detections

Analytics