CVE-2021-45956

Fuzzing crash via print_mac heap overwrite

Published Dec 31, 2021 · Updated Oct 28, 2024

A reported heap-buffer overflow in Simon Kelley dnsmasq 2.86 crashes an OSS-Fuzz build in the DHCP reply logging path. The print_mac function performs a four-byte out-of-bounds write after calls from log_packet and dhcp_reply in the fuzz harness. The maintainer disputes real-world reachability and requested cancellation, while an upstream contributor attributed the crash family to incomplete fuzzer initialization; no deployable consequence has been established.

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 reported heap-buffer overflow in Simon Kelley dnsmasq 2.86 crashes an OSS-Fuzz build in the DHCP reply logging path. The print_mac function performs a four-byte out-of-bounds write after calls from log_packet and dhcp_reply in the fuzz harness. The maintainer disputes real-world reachability and requested cancellation, while an upstream contributor attributed the crash family to incomplete fuzzer initialization; no deployable consequence has been established.

The record

CVE
CVE-2021-45956
Published
Dec 31, 2021
Updated
Oct 28, 2024
Vendor
Simon Kelley
Product
dnsmasq
Classifications
CWE-787
Attack vector
Unavailable
Privileges
Unavailable

Timeline

How it unfolded

  1. Dec 31, 2021CVE publishedPublication date reported by the CVE source.
  2. Oct 28, 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?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=2.86

What conditions does exploitation require?

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

What is affected?

Simon Kelley · dnsmasqversion=2.86

Published CVSS scores

9.8CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
6.5SUSECVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L
9.8NVDCVSS: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.

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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)
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.

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Technologies

Your stack

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Your stack

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