Security Bypass Affecting dnsmasq package, versions [,2.83)


Severity

Recommended
0.0
low
0
10

CVSS assessment made by Snyk's Security Team. Learn more

Threat Intelligence

EPSS
0.44% (75th percentile)

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  • Snyk IDSNYK-UNMANAGED-DNSMASQ-2335704
  • published12 Jan 2022
  • disclosed20 Jan 2021
  • creditUnknown

Introduced: 20 Jan 2021

CVE-2020-25685  (opens in a new tab)
CWE-358  (opens in a new tab)

How to fix?

Upgrade dnsmasq to version 2.83 or higher.

Overview

Affected versions of this package are vulnerable to Security Bypass. A flaw was found in dnsmasq before version 2.83. 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 with CVE-2020-25684 the attack complexity of a successful attack is reduced. The highest threat from this vulnerability is to data integrity.

CVSS Scores

version 3.1