What’s Vulnerable › Vulnerabilities
CVE-2020-25686
- Severity: low (CVSS 3.7 v3.1)
- Exploited in the wild: not listed in CISA KEV
- EPSS: 5.5% 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-358
Description
A flaw was found in dnsmasq before version 2.83. When receiving a query, dnsmasq does not check for an existing pending request for the same name and forwards a new request. By default, a maximum of 150 pending queries can be sent to upstream servers, so there can be at most 150 queries for the same name. This flaw allows an off-path attacker on the network to substantially reduce the number of attempts that it would have to perform to forge a reply and have it accepted by dnsmasq. This issue is mentioned in the "Birthday Attacks" section of RFC5452. If chained with CVE-2020-25684, the attack complexity of a successful attack is reduced. The highest threat from this vulnerability is to data integrity.
Affected products
- Arista Networks EOS: from 4.21 before 4.21.14m; from 4.22 before 4.22.9m; from 4.23 before 4.23.7m; from 4.24 before 4.24.5m; from 4.25 before 4.25.2f — fixed in 4.21.14m, 4.22.9m, 4.23.7m, 4.24.5m, 4.25.2f
- Debian Linux: 10.0
- Fedoraproject Fedora: 32, 33
- Simon Kelley dnsmasq: before 2.83 — fixed in 2.83
How to fix
Upgrade to a fixed version: Arista Networks EOS 4.21.14m, 4.22.9m, 4.23.7m, 4.24.5m; Simon Kelley dnsmasq 2.83. Check the vendor advisory for mitigations.
References
- https://bugzilla.redhat.com/show_bug.cgi?id=1890125
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QGB7HL3OWHTLEPSMLDGOMXQKG3KM2QME/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/WYW3IR6APUSKOYKL5FT3ACTIHWHGQY32/
- https://security.gentoo.org/glsa/202101-17
- https://www.arista.com/en/support/advisories-notices/security-advisories/12135-security-advisory-61
- https://www.debian.org/security/2021/dsa-4844
- https://www.jsof-tech.com/disclosures/dnspooq/
- https://bugzilla.redhat.com/show_bug.cgi?id=1890125
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QGB7HL3OWHTLEPSMLDGOMXQKG3KM2QME/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/WYW3IR6APUSKOYKL5FT3ACTIHWHGQY32/
- https://security.gentoo.org/glsa/202101-17
- https://www.arista.com/en/support/advisories-notices/security-advisories/12135-security-advisory-61
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