CVE-2020-25685
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 v3.1
- 3.7 LOW
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N - CVSS v2.0
- 4.3 MEDIUM
AV:N/AC:M/Au:N/C:N/I:P/A:N - EPSS
- 2.18% chance of exploitation in the next 30 days, 81th percentile
- Published
- 2021-01-20
- Updated
- 2025-11-04
Proof-of-concept exploits (1)
- knqyf263/dnspooq101★ · 2021-01-24