CVE & CISA-KEV Catalog

CVE-2020-25685

LOWEPSS 80th pctl
3.7
CVSS v3
NVD

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.

CWE-326

How to fix

Remediation Available
dnsmasqDebian
Fixed in:2.83-1CVE-2020-25685
Fixed in:2.83-1CVE-2020-25685
Fixed in:2.83-1CVE-2020-25685
Fixed in:2.83-1CVE-2020-25685
dnsmasqUbuntu
Fixed in:2.75-1ubuntu0.16.04.7USN-4698-1
Fixed in:2.79-1ubuntu0.2USN-4698-1
Fixed in:2.80-1.1ubuntu1.2USN-4698-1
dnsmasq-baseUbuntu
Fixed in:2.75-1ubuntu0.16.04.7USN-4698-1
Fixed in:2.79-1ubuntu0.2USN-4698-1
Fixed in:2.80-1.1ubuntu1.2USN-4698-1
dnsmasq-utilsUbuntu
Fixed in:2.75-1ubuntu0.16.04.7USN-4698-1
Fixed in:2.79-1ubuntu0.2USN-4698-1
Fixed in:2.80-1.1ubuntu1.2USN-4698-1

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork
Attack ComplexityHigh
Privileges RequiredNone
User InteractionNone
ScopeUnchanged

Impact

ConfidentialityNone
IntegrityLow
AvailabilityNone

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N

Exploit Intelligence

2.18%probability of exploitation in 30 days
80thpercentile

Elevated risk: more likely to be exploited than 80% of all known CVEs.

References

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Markdown

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HTML

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2025-11-04.