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Vulnerability · Published Jan 20, 2021 · Assigned by redhat

CVE-2020-25685

Low 3.7

In plain English

A low-severity security flaw in dnsmasq. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 2.2% (higher than 83% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS NVD)3.7Low
Exploit odds (30 days)2.2%top 17.2% of all CVEs
Exploited in the wildNo reportsnot in CISA KEV
Attack toolingNoneno public tooling known

Official description

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.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Alpine:v3.20dnsmasq2.83-r0ALPINE-CVE-2020-25685
Alpine:v3.21dnsmasq2.83-r0ALPINE-CVE-2020-25685
Alpine:v3.22dnsmasq2.83-r0ALPINE-CVE-2020-25685
Alpine:v3.23dnsmasq2.83-r0ALPINE-CVE-2020-25685
Alpine:v3.24dnsmasq2.83-r0ALPINE-CVE-2020-25685
Debian:12dnsmasq2.83-1DEBIAN-CVE-2020-25685
Debian:13dnsmasq2.83-1DEBIAN-CVE-2020-25685
Debian:14dnsmasq2.83-1DEBIAN-CVE-2020-25685

Affected products (as reported)

VendorProductVersions
n/a dnsmasq dnsmasq 2.83

Weakness: CWE-326

References