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Fencer Vulns
critical 9.8

CVE-2021-45955 json

Dnsmasq 2.86 has a heap-based buffer overflow in resize_packet (called from FuzzResizePacket and fuzz_rfc1035.c) because of the lack of a p…

published 2021-12-31 4 y ago modified 2026-06-17 4 mo ago also EUVD-2021-32662

cvss
9.8
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
2.6%
EPSS 2.6% chance of exploitation in 30 days, percentile 85%
public exploits
0
none known

Summary

Dnsmasq 2.86 has a heap-based buffer overflow in resize_packet (called from FuzzResizePacket and fuzz_rfc1035.c) because of the lack of a proper bounds check upon pseudo header re-insertion. NOTE: the vendor's position is that CVE-2021-45951 through CVE-2021-45957 "do not represent real vulnerabilities, to the best of our knowledge." However, a contributor states that a security patch (mentioned in 016162.html) is needed

Patch / fix

  • dnsmasq CBL-Mariner 2.0 2.89-2

azure linux advisories AZL-8962

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2021-45955 updated cvss 0.0

dnsmasq: heap-based buffer overflow in resize_packet

  • Red Hat Enterprise Linux 6 dnsmasq, dnsmasq-utils Red Hat Enterprise Linux 7 dnsmasq, dnsmasq-utils Red Hat Enterprise Linux 8 dnsmasq, dnsmasq-utils Red Hat Enterprise Linux 9 dnsmasq, dnsmasq-utils Red Hat OpenStack Platform 13 (Queens) dnsmasq-utils
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
Proof of concept is public
Automatable
yes
Technical impact
total
Assessed
2 y ago

Exploit prediction

2.60% chance of exploitation in the next 30 days, higher than 85% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • bugs.chromium.org https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=35898 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
NVD 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 7.5 AV:N/AC:L/Au:N/C:P/I:P/A:P

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.