CVE-2021-45953Network attack vector

Service crash via disputed extract_name heap overwrite

Published Dec 31, 2021 · Updated Aug 4, 2024

A disputed heap buffer overflow in dnsmasq 2.86 allows remote attackers to crash the service through crafted DNS data. The OSS-Fuzz harness passes extract_name an undersized heap buffer through hash_questions, and the function writes one byte beyond the allocation. The upstream maintainer states that incomplete fuzzer initialization creates the condition and that the affected code receives an adequate buffer in real deployments.

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

What happened

A disputed heap buffer overflow in dnsmasq 2.86 allows remote attackers to crash the service through crafted DNS data. The OSS-Fuzz harness passes extract_name an undersized heap buffer through hash_questions, and the function writes one byte beyond the allocation. The upstream maintainer states that incomplete fuzzer initialization creates the condition and that the affected code receives an adequate buffer in real deployments.

The record

CVE
CVE-2021-45953
Published
Dec 31, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-787
Attack vector
network
Privileges
unauthenticated

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

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

9.8NIST National Vulnerability DatabaseCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
7.5NIST National Vulnerability DatabaseAV:N/AC:L/Au:N/C:P/I:P/A:P

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-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

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Your stack

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