CVE-2021-45951

Disputed heap overwrite during fuzz testing

Published Dec 31, 2021 · Updated Aug 4, 2024

A reported heap-based buffer overflow in dnsmasq 2.86 occurs in check_bad_address during OSS-Fuzz harness testing. The harness produced a one-byte heap overwrite when check_for_bogus_wildcard called check_bad_address, but no production input path was established. The dnsmasq maintainer disputes the report, and Debian, Red Hat, and Ubuntu classify it as a non-issue or unaffected.

CVSS severity9.8
Critical
EPSS probability2.59%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

A reported heap-based buffer overflow in dnsmasq 2.86 occurs in check_bad_address during OSS-Fuzz harness testing. The harness produced a one-byte heap overwrite when check_for_bogus_wildcard called check_bad_address, but no production input path was established. The dnsmasq maintainer disputes the report, and Debian, Red Hat, and Ubuntu classify it as a non-issue or unaffected.

The record

CVE
CVE-2021-45951
Published
Dec 31, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-787
Attack vector
Unavailable
Privileges
Unavailable

Timeline

How it unfolded

  1. Dec 31, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectorUnavailable in this record.
Required privilegesUnavailable in this record.

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

9.8UbuntuCVSS:3.1/AV:N/AC:L/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.

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)
VectorUnavailable
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-787Out-of-bounds Write

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

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo