CVE-2020-25681Network attack vector

Code execution via DNSSEC RRset sorting overflow

Published Jan 20, 2021 · Updated Nov 4, 2025

Heap-based buffer overflow in dnsmasq before 2.83 allows remote attackers to execute code through forged DNSSEC replies. During DNSSEC validation, sort_rrset sorts attacker-controlled resource-record sets into a heap buffer without enforcing its allocation boundary. DNSSEC must be compiled in and enabled, and the attacker must forge an upstream reply accepted for an outstanding query; exploitation can crash the daemon or execute code.

CVSS severity8.1
High
EPSS probability81.19%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Heap-based buffer overflow in dnsmasq before 2.83 allows remote attackers to execute code through forged DNSSEC replies. During DNSSEC validation, sort_rrset sorts attacker-controlled resource-record sets into a heap buffer without enforcing its allocation boundary. DNSSEC must be compiled in and enabled, and the attacker must forge an upstream reply accepted for an outstanding query; exploitation can crash the daemon or execute code.

The record

CVE
CVE-2020-25681
Published
Jan 20, 2021
Updated
Nov 4, 2025
Vendor
Simon Kelley
Product
dnsmasq
Classifications
CWE-122, T1190
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

8.1UbuntuCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

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.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-122Heap-based Buffer Overflow
T1190Exploit Public-Facing Application

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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