CVE-2020-25684Network attack vector

DNS cache poisoning via loose reply matching

Published Jan 20, 2021 · Updated Nov 4, 2025

DNS cache poisoning in dnsmasq before 2.83 allows remote attackers to redirect DNS clients through forged replies accepted by the forwarder. The forward.c reply_query() path checks whether an address and port belong to any pending query but does not bind them to the exact query being answered. Exploitation requires flooding forged UDP replies while a forwarded query is pending; a successful forgery inserts attacker-chosen DNS data into the cache.

CVSS severity4.0
Medium
EPSS probability4.04%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

DNS cache poisoning in dnsmasq before 2.83 allows remote attackers to redirect DNS clients through forged replies accepted by the forwarder. The forward.c reply_query() path checks whether an address and port belong to any pending query but does not bind them to the exact query being answered. Exploitation requires flooding forged UDP replies while a forwarded query is pending; a successful forgery inserts attacker-chosen DNS data into the cache.

The record

CVE
CVE-2020-25684
Published
Jan 20, 2021
Updated
Nov 4, 2025
Vendor
Simon Kelley
Product
dnsmasq
Classifications
CWE-358, T1565.002
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 20, 2021CVE publishedPublication date reported by the CVE source.
  2. Nov 4, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=dnsmasq 2.83

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Simon Kelley · dnsmasqversion=dnsmasq 2.83

Published CVSS scores

3.7NVDCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
4.0Red HatCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-358Improperly Implemented Security Check for Standard
T1565.002Transmitted Data Manipulation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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