How severe is CVE-2021-45955?

CVE-2021-45955 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-45955 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (83rd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-45955?

CVE-2021-45955 affects Thekelleys Dnsmasq. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-45955?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2021-45955 published?

CVE-2021-45955 was published on 2022-01-01 and last updated on 2026-06-17.

CVE-2021-45955

CVE-2021-45955 is a critical-severity vulnerability in Thekelleys Dnsmasq with a CVSS 3.x base score of 9.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-787.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 7.5
EPSS exploit prediction: 3% (83rd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-787
Affected product: Thekelleys Dnsmasq
Published: 2022-01-01
Last modified: 2026-06-17

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

Frequently asked questions

What is CVE-2021-45955?: 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
How severe is CVE-2021-45955?: CVE-2021-45955 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-45955 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (83rd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-45955?: CVE-2021-45955 affects Thekelleys Dnsmasq. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-45955?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2021-45955 published?: CVE-2021-45955 was published on 2022-01-01 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:thekelleys:dnsmasq:2.86:*:*:*:*:*:*:*

More vulnerabilities in Thekelleys Dnsmasq

CVE-2021-45957 — Critical (CVSS 9.8): Dnsmasq 2.86 has a heap-based buffer overflow in answer_request (called from FuzzAnswerTheRequest and fuzz_rfc1035.c).…
CVE-2021-45956 — Critical (CVSS 9.8): Dnsmasq 2.86 has a heap-based buffer overflow in print_mac (called from log_packet and dhcp_reply). NOTE: the vendor's…
CVE-2021-45954 — Critical (CVSS 9.8): Dnsmasq 2.86 has a heap-based buffer overflow in extract_name (called from answer_auth and FuzzAuth). NOTE: the…
CVE-2021-45953 — Critical (CVSS 9.8): Dnsmasq 2.86 has a heap-based buffer overflow in extract_name (called from hash_questions and fuzz_util.c). NOTE: the…
CVE-2021-45952 — Critical (CVSS 9.8): Dnsmasq 2.86 has a heap-based buffer overflow in dhcp_reply (called from dhcp_packet and FuzzDhcp). NOTE: the vendor's…
CVE-2021-45951 — Critical (CVSS 9.8): Dnsmasq 2.86 has a heap-based buffer overflow in check_bad_address (called from check_for_bogus_wildcard and…

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