CVE-2021-45956
Dnsmasq 2.86 has a heap-based buffer overflow in print_mac (called from log_packet and dhcp_reply).
Dnsmasq 2.86 has a heap-based buffer overflow in print_mac (called from log_packet and dhcp_reply). 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.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- High
- Integrity
- High
- Availability
- High
Exploit likelihood
What each source reports
NVD Score used
Dnsmasq 2.86 has a heap-based buffer overflow in print_mac (called from log_packet and dhcp_reply). 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.
- Record
CVE-2021-45956- CVSS 3.1
- 9.8 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - CVSS 2.0
- 7.5 High
AV:N/AC:L/Au:N/C:P/I:P/A:P - Weakness
- CWE-787
- Updated
- 2026-11-02
CVE List
Dnsmasq 2.86 has a heap-based buffer overflow in print_mac (called from log_packet and dhcp_reply). 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.
- Record
CVE-2021-45956- CVSS 3.1
- 9.8 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - Weakness
- CWE-787
- Updated
- 2026-11-02
EUVDEUVD-2021-32663
Dnsmasq 2.86 has a heap-based buffer overflow in print_mac (called from log_packet and dhcp_reply). 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.
- Record
EUVD-2021-32663- CVSS 3.1
- 9.8 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - Updated
- 2026-11-03
GitHub AdvisoriesGHSA-c76g-xw7w-9qj6
Dnsmasq 2.86 has a heap-based buffer overflow in print_mac (called from log_packet and dhcp_reply).
Dnsmasq 2.86 has a heap-based buffer overflow in print_mac (called from log_packet and dhcp_reply).
- Record
GHSA-c76g-xw7w-9qj6- CVSS 3.1
- 9.8 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - Weakness
- CWE-122, CWE-787
- Updated
- 2026-11-02
OSVAZL-8963
CVE-2021-45956 affecting package dnsmasq for versions less than 2.89-1
Dnsmasq 2.86 has a heap-based buffer overflow in print_mac (called from log_packet and dhcp_reply). 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.
- Record
AZL-8963- CVSS 3.1
- 9.8 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - Updated
- 2026-11-02
OSVBELL-CVE-2021-45956
CVE-2021-45956 does not affect BellSoft software
- Record
BELL-CVE-2021-45956- CVSS 3.1
- 9.8 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
dnsmasqAzure Linux:2 |
before 2.89-1 | 2.89-1 |
History
| Recorded | Changed | Sources |
|---|---|---|
| aliases | EUVD | |
| first indexed | CVE List, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2021-45956 is a critical vulnerability (CVSS 9.8) in Thekelleys Dnsmasq, published December 31, 2021. Its validity is disputed. EPSS puts the chance of exploitation in the next 30 days at 2.71%, the 86th percentile. Fixed in dnsmasq 2.89-1.
References
github.com/google/oss-fuzz-vulns/blob/main/vulns/dnsmasq/OSV-2021-933.yaml
bugs.chromium.org/p/oss-fuzz/issues/detail?id=35887
lists.thekelleys.org.uk/pipermail/dnsmasq-discuss/2022q1/016162.html
nvd.nist.gov/vuln/detail/CVE-2021-45956
docs.bell-sw.com/security/cves/CVE-2021-45956