Vulnerability Description
A flaw was found in dnsmasq before version 2.83. When getting a reply from a forwarded query, dnsmasq checks in forward.c:reply_query(), which is the forwarded query that matches the reply, by only using a weak hash of the query name. Due to the weak hash (CRC32 when dnsmasq is compiled without DNSSEC, SHA-1 when it is) this flaw allows an off-path attacker to find several different domains all having the same hash, substantially reducing the number of attempts they would have to perform to forge a reply and get it accepted by dnsmasq. This is in contrast with RFC5452, which specifies that the query name is one of the attributes of a query that must be used to match a reply. This flaw could be abused to perform a DNS Cache Poisoning attack. 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.
CVSS Score
LOW
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Thekelleys | Dnsmasq | < 2.83 |
| Fedoraproject | Fedora | 32 |
| Debian | Debian Linux | 10.0 |
| Arista | Eos | >= 4.21, < 4.21.14m |
Related Weaknesses (CWE)
References
- https://bugzilla.redhat.com/show_bug.cgi?id=1889688Issue TrackingPatchThird Party Advisory
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedorapro
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedorapro
- https://security.gentoo.org/glsa/202101-17Third Party Advisory
- https://www.arista.com/en/support/advisories-notices/security-advisories/12135-sThird Party Advisory
- https://www.debian.org/security/2021/dsa-4844Third Party Advisory
- https://www.jsof-tech.com/disclosures/dnspooq/Third Party Advisory
- https://bugzilla.redhat.com/show_bug.cgi?id=1889688Issue TrackingPatchThird Party Advisory
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedorapro
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedorapro
- https://security.gentoo.org/glsa/202101-17Third Party Advisory
- https://www.arista.com/en/support/advisories-notices/security-advisories/12135-sThird Party Advisory
- https://www.debian.org/security/2021/dsa-4844Third Party Advisory
- https://www.jsof-tech.com/disclosures/dnspooq/Third Party Advisory
- https://www.kb.cert.org/vuls/id/434904
FAQ
What is CVE-2020-25685?
CVE-2020-25685 is a vulnerability with a CVSS score of 3.7 (LOW). A flaw was found in dnsmasq before version 2.83. When getting a reply from a forwarded query, dnsmasq checks in forward.c:reply_query(), which is the forwarded query that matches the reply, by only us...
How severe is CVE-2020-25685?
CVE-2020-25685 has been rated LOW with a CVSS base score of 3.7/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2020-25685?
Check the references section above for vendor advisories and patch information. Affected products include: Thekelleys Dnsmasq, Fedoraproject Fedora, Debian Debian Linux, Arista Eos.