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CVE Record

CVE-2020-25687: A flaw was found in dnsmasq before version 2.83.

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.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

CVE-2020-25687 is a dnsmasq DNSSEC parsing flaw that can crash affected resolvers. An attacker able to produce valid DNS replies may trigger a heap buffer overflow before DNSSEC validation completes. The documented business impact is service disruption, especially where dnsmasq provides local DNS for networks or devices.

Executive priority

Treat this as a priority availability risk for environments relying on dnsmasq for DNS resolution. It is not KEV-listed in the supplied data, but a resolver crash can disrupt network access, authentication flows, updates, and device connectivity.

Technical view

In dnsmasq before 2.83, missing length checks in rfc1035.c extract_name() can cause sort_rrset() to call memcpy() with a negative size when DNSSEC is enabled. The reported outcome is heap memory corruption and dnsmasq crash, resulting in denial of service. The source bundle does not establish remote code execution.

Likely exposure

Exposure is most likely on Linux systems, network appliances, or embedded devices running dnsmasq before 2.83 with DNSSEC enabled. Asset owners should verify packaged dnsmasq versions because distributions may backport fixes without changing to upstream 2.83 exactly.

Exploitation context

CISA KEV status is false in the bundle, and no cited source in the bundle confirms active exploitation. Exploitation requires an attacker who can create valid DNS replies reaching the vulnerable dnsmasq instance while DNSSEC processing is enabled.

Researcher notes

The strongest source details point to CWE-122 heap overflow in DNSSEC handling, caused by insufficient length checks before DNSSEC validation. The bundle supports denial-of-service impact, not confirmed code execution or active exploitation. Validate exposure by combining version checks, DNSSEC configuration, and distribution-specific patch backport evidence.

Mitigation direction

  • Apply vendor dnsmasq security updates or upgrade to a fixed release.
  • Prioritize systems where dnsmasq handles DNS for many users or critical networks.
  • If patching is delayed, review vendor guidance for DNSSEC-related workarounds.
  • Restrict unnecessary exposure of DNS services to untrusted networks.
  • Track distribution advisories for backported fixes and package status.

Validation and detection

  • Inventory dnsmasq deployments and record package versions.
  • Confirm whether DNSSEC is enabled on each dnsmasq instance.
  • Check vendor advisory status for the installed distribution package.
  • Verify updated systems include fixes for CVE-2020-25687.
  • Monitor dnsmasq crashes or abnormal DNS service restarts.
Prepared
Confidence
high
Sources
7

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cwe · low confidence lookup

CWE-122: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

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cve · low confidence lookup

CVE-2020-25687 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
0Timeline events
0ADP providers
9Source links

CVSS and timeline data

No CVSS vectors or timeline events were available in the normalized CVE source material.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
n/adnsmasqdnsmasq 2.83Listed
Weakness

CWE details

CWE-122

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.

CWE-122 · source CWE mapping

Heap-based Buffer Overflow

Heap-based Buffer Overflow represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs