CVE-2020-25682
HighA buffer overflow vulnerability was discovered in the way dnsmasq extract names from DNS packets before validating them with DNSSEC data.
Published Jan 21, 2021 · Updated Aug 5, 2026 · Also known as ALPINE-CVE-2020-25682, DEBIAN-CVE-2020-25682, UBUNTU-CVE-2020-25682
Key Facts
Patch immediately- CVE-2020-25682 is a high-severity vulnerability (CVSS 8.1 v3.1) affecting Dnsmasq (Thekelleys), Debian Linux, Fedora (Fedoraproject) and 1 more product.
- It is not listed in any known-exploited vulnerabilities catalog. No public exploit code is known.
- EPSS estimates a 71% probability of exploitation in the next 30 days.
- Fixed versions are available, including Dnsmasq 0:2.79-11.el8_2.2, Dnsmasq 2.75-1ubuntu0.16.04.7, Dnsmasq 2.76-17.0.3.el7_9.3.
- Brandefense priority: patch immediately, because it is very likely to be exploited soon.
CVSS v3.1
8.1
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS (30-day exploit likelihood)
71%
Higher than 99.3% of all scored CVEs
Exploited in the wild
No known
Not in a known-exploited catalog
Public exploit code
None known
Get the full CVE-2020-25682 brief as a PDF
Every affected product and fixed release, exploitation status and a first 24 hours response checklist, emailed within minutes.
Description
A flaw was found in dnsmasq before 2.83. A buffer overflow vulnerability was discovered in the way dnsmasq extract names from DNS packets before validating them with DNSSEC data. An attacker on the network, who can create valid DNS replies, could use this flaw to cause an overflow with arbitrary data in a heap-allocated memory, possibly executing code on the machine. The flaw is in the rfc1035.c:extract_name() function, which writes data to the memory pointed by name assuming MAXDNAME*2 bytes are available in the buffer. However, in some code execution paths, it is possible extract_name() gets passed an offset from the base buffer, thus reducing, in practice, the number of available bytes that can be written in the buffer. The highest threat from this vulnerability is to data confidentiality and integrity as well as system availability.
Affected Products
107 affected entries in total| Product | Affected versions | Fixed in |
|---|---|---|
| DnsmasqThekelleys | >= dnsmasq 2.83 | 2.83 |
| Debian LinuxDebian | 10.0, 9.0 | n/a |
| FedoraFedoraproject | 32, 33 | n/a |
| dnsmasq-utilsoracle | See advisory | 2.76-17.0.3.el7_9.3 |
Patched Releases
Dnsmasq
0:2.79-11.el8_2.2, 2.75-1ubuntu0.16.04.7, 2.76-17.0.3.el7_9.3, 2.76-5+deb9u3, 2.78-0.16.14.1, 2.78-0.17.15.1, 2.78-18.15.1, 2.78-3.11.1, 2.78-7.6.1, 2.78-lp151.5.6.1, 2.78-lp152.7.3.1, 2.79-13.el8_3.1, 2.79-1ubuntu0.2, 2.80-1.1ubuntu1.2, 2.80-1+deb10u1, 2.82-1.ph1, 2.82-1.ph2, 2.82-1.ph3, 2.83-1, 2.83-r0, 2.85-1, 2.83
dnsmasq-utils
2.76-17.0.3.el7_9.3, 2.78-18.15.1, 2.78-lp151.5.6.1, 2.78-lp152.7.3.1, 2.79-13.el8_3.1
Timeline
Publicly disclosed
Jan 21, 2021
Last updated
Aug 5, 2026
Weakness Type
- CWE-122 Heap-based Buffer Overflow
- CWE-787 Out-of-bounds Write
References
- advisoryhttp://lists.thekelleys.org.uk/pipermail/dnsmasq-discuss/2021q1/014599.html
- advisoryRHSA-2021:0150
- advisoryRHSA-2021:0151
- advisoryRHSA-2021:0152
- advisoryhttps://access.redhat.com/security/vulnerabilities/RHSB-2021-001
FAQ
Common Questions.
A flaw was found in dnsmasq before 2.83.
Affected: Dnsmasq (Thekelleys) versions >= dnsmasq 2.83; Debian Linux versions 10.0, 9.0; Fedora (Fedoraproject) versions 32, 33, among others. The full list is in the CVE brief.
It is not listed in any known-exploited vulnerabilities catalog.
No, it is not currently listed in the CISA Known Exploited Vulnerabilities catalog.
No public exploit code is known.
Fixed versions are available, including Dnsmasq 0:2.79-11.el8_2.2, Dnsmasq 2.75-1ubuntu0.16.04.7, Dnsmasq 2.76-17.0.3.el7_9.3.
Brandefense priority: patch immediately, because it is very likely to be exploited soon.
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