Skip to main content
No exploitation reportedFix available

CVE-2020-25687

No exploitation reported by the sources we read.

  • Published2021-01-20
  • WeaknessCWE-122

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

A flaw was found in dnsmasq before version 2.83. A heap-based buffer overflow was discovered in dnsmasq when DNSSEC is enabled and before it validates the received DNS entries. This flaw allows a remote attacker, who can create valid DNS replies, to cause an overflow in a heap-allocated memory. This flaw is caused by the lack of length checks in rfc1035.c:extract_name(), which could be abused to make the code execute memcpy() with a negative size in sort_rrset() and cause a crash in dnsmasq, resulting in a denial of service. The highest threat from this vulnerability is to system availability.

Timeline

dates in UTC
  1. 2021-01-2017:15CVE publishedNVD
  2. 2026-10-2319:23EPSS crossed 10 %FIRST EPSS

Observed activity

isMalicious corpus · updated 2026-10-23 18:48 UTC
Indicators tagged with this CVE, per day0 indicators over 7 days
Block these indicators
  • Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2020-25687?format=txt
  • CSV export: https://api.ismalicious.com/edl/cve/CVE-2020-25687?format=csv
  • TAXII collection of exploited CVEs
  • The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD
Debian debian linux
BranchAffectedFixed in
9.0= 9.0no fix published
10.0= 10.0no fix published
Fedoraproject fedora
BranchAffectedFixed in
32.x= 32no fix published
33.x= 33no fix published
Thekelleys dnsmasq
BranchAffectedFixed in
2.83< 2.832.83

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

Advisories and patches

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof-of-concept repositories
none listed
PoC-in-GitHub

Sources

  • NVDCVSS 3.15.9read 2026-10-23
  • NVDCVSS 2.07.1read 2026-10-23
  • CNAweakness (CWE)CWE-122read 2026-10-23
  • FIRST EPSSEPSS score89.3 %read 2026-10-23

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Published
2021-01-20
Last Modified
2026-06-17
NVD status
Modified

Frequently asked questions

What is CVE-2020-25687?

A flaw was found in dnsmasq before version 2.83. A heap-based buffer overflow was discovered in dnsmasq when DNSSEC is enabled and before it validates the received DNS entries. This flaw allows a remote attacker, who can create valid DNS replies, to cause an overflow in a heap-allocated memory. This flaw is caused by the lack of length checks in rfc1035.c:extract_name(), which could be abused to make the code execute memcpy() with a negative size in sort_rrset() and cause a crash in dnsmasq, resulting in a denial of service. The highest threat from this vulnerability is to system availability.

Is CVE-2020-25687 actively exploited?

Active exploitation of CVE-2020-25687 has not been confirmed. Its EPSS score was 89.3% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2020-25687?

CVE-2020-25687 has a CVSS v3 base score of 5.9 (MEDIUM severity), with vector string CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H.

Hear about the next vulnerability in your software

Surveillance reads the versions in your stack — a domain, a lockfile or a list — checks each CVE against the ranges its sources publish, and alerts you when one you run is exploited or enters CISA KEV. A version it cannot read stays « version not verified ».

Get alerts for this productCISA KEV additions, October 2026Search CVEs

No credit card required · No monthly cap on website lookups · 250 API requests/month

Go further

Related vulnerabilities

Same product first, then the same vendor advisory and the same publication week.

Back to CVE Database