CVE-2020-25682Network attack vector

Remote code execution via DNS name extraction overflow

Published Jan 20, 2021 · Updated Nov 4, 2025

Heap-based buffer overflow in dnsmasq before 2.83 allows remote attackers to execute code or disrupt service via crafted DNS replies. The rfc1035.c extract_name() function writes up to MAXDNAME*2 bytes without accounting for an offset into the packet buffer, so DNSSEC validation can overrun heap memory. The flaw requires a DNSSEC-enabled build and an attacker able to supply or inject accepted DNS replies; an internal-network attacker or open resolver can trigger it without user interaction.

CVSS severity8.1
High
EPSS probability70.75%
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 or disrupt service via crafted DNS replies. The rfc1035.c extract_name() function writes up to MAXDNAME*2 bytes without accounting for an offset into the packet buffer, so DNSSEC validation can overrun heap memory. The flaw requires a DNSSEC-enabled build and an attacker able to supply or inject accepted DNS replies; an internal-network attacker or open resolver can trigger it without user interaction.

The record

CVE
CVE-2020-25682
Published
Jan 20, 2021
Updated
Nov 4, 2025
Vendor
Simon Kelley
Product
dnsmasq
Classifications
CWE-122, CWE-787, 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

8.1NVDCVSS: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
CWE-787Out-of-bounds Write
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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