CVE-2020-25683

Severity: medium (CVSS 5.9 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 88.7% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-01-20 · updated 2026-06-17
Weakness: CWE-122

Description

A flaw was found in dnsmasq before version 2.83. A heap-based buffer overflow was discovered in dnsmasq when DNSSEC is enabled and before it validates the received DNS entries. A remote attacker, who can create valid DNS replies, could use this flaw to cause an overflow in a heap-allocated memory. This flaw is caused by the lack of length checks in rfc1035.c:extract_name(), which could be abused to make the code execute memcpy() with a negative size in get_rdata() and cause a crash in dnsmasq, resulting in a denial of service. The highest threat from this vulnerability is to system availability.

Affected products

Debian Linux: 9.0, 10.0
Fedoraproject Fedora: 32, 33
Simon Kelley dnsmasq: before 2.83 — fixed in 2.83

How to fix

Upgrade to a fixed version: Simon Kelley dnsmasq 2.83. Check the vendor advisory for mitigations.

References

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