CVE-2020-25687

CVE-2020-25687 is a medium-severity vulnerability in Thekelleys Dnsmasq with a CVSS 3.x base score of 5.9. Its EPSS exploit-prediction score of 87% places it in the 100th percentile, indicating an elevated likelihood of exploitation. The underlying weakness is classified as CWE-122.

Key facts

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. This flaw allows a remote attacker, who can create valid DNS replies, 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 sort_rrset() and cause a crash in dnsmasq, resulting in a denial of service. The highest threat from this vulnerability is to system availability.

Frequently asked questions

What is CVE-2020-25687?
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. This flaw allows a remote attacker, who can create valid DNS replies, 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 sort_rrset() and cause a crash in dnsmasq, resulting in a denial of service. The highest threat from this vulnerability is to system availability.
How severe is CVE-2020-25687?
CVE-2020-25687 has a CVSS 3.x base score of 5.9, rated medium severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2020-25687 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 87% (100th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2020-25687?
CVE-2020-25687 primarily affects Thekelleys Dnsmasq. In total, 5 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2020-25687?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2020-25687 published?
CVE-2020-25687 was published on 2021-01-20 and last updated on 2026-06-17.

References

Affected products (5)

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