CVE-2021-45955

Name: CVE-2021-45955
Creator: NVD / NIST
Published: 2022-01-01T00:15:08.677+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

CRITICALCVSS 9.8/10EPSS 2.52%

Last modified Jun 17, 2026

CVE-2021-45955 is a critical-severity vulnerability rated 9.8/10 on the CVSS scale. 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. EPSS estimates a 2.52% chance of exploitation in the next 30 days.

Description

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

Metrics

CVSS 3.1

9.8/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS Probability

2.52%

82.8th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-787

Affected Software

Vendor	Product	Versions
Thekelleys	Dnsmasq	2.86

References

https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=35898Exploit, Issue Tracking, Third Party Advisory
https://github.com/google/oss-fuzz-vulns/blob/main/vulns/dnsmasq/OSV-2021-932.yamlThird Party Advisory
https://lists.thekelleys.org.uk/pipermail/dnsmasq-discuss/2022q1/016162.htmlMailing List, Third Party Advisory
https://lists.thekelleys.org.uk/pipermail/dnsmasq-discuss/2022q1/016164.htmlMailing List, Third Party Advisory
https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=35898Exploit, Issue Tracking, Third Party Advisory
https://github.com/google/oss-fuzz-vulns/blob/main/vulns/dnsmasq/OSV-2021-932.yamlThird Party Advisory
https://lists.thekelleys.org.uk/pipermail/dnsmasq-discuss/2022q1/016162.htmlMailing List, Third Party Advisory
https://lists.thekelleys.org.uk/pipermail/dnsmasq-discuss/2022q1/016164.htmlMailing List, Third Party Advisory

Timeline

Published: Jan 1, 2022
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-45955?

How severe is CVE-2021-45955?

CVE-2021-45955 has a CVSS score of 9.8/10 (CRITICAL severity). The EPSS model estimates a 2.52% probability of exploitation in the next 30 days.

How do I fix CVE-2021-45955?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-45955?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST