LowFix available
dnsmasq — security advisory
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.
- Products
- dnsmasq
- Affected versions
- Not specified
- Fixed versions
- 2.83-r0
- CVEs
- CVE-2020-25685
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 1 Nov 2026, 12:08 UTC · Revision 1
Source evidence
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.
osv:ALPINE-CVE-2020-25685
dnsmasq
Fixed versions: 2.83-r0
dnsmasq
Fixed versions: 2.83-r0
dnsmasq
Fixed versions: 2.83-r0
dnsmasq
Fixed versions: 2.83-r0
dnsmasq
Fixed versions: 2.83-r0
dnsmasq
Fixed versions: 2.83-r0
dnsmasq
Fixed versions: 2.83-r0
dnsmasq
Fixed versions: 2.83-r0
dnsmasq
Fixed versions: 2.83-r0
dnsmasq
Fixed versions: 2.83-r0
dnsmasq
Fixed versions: 2.83-r0
dnsmasq
Fixed versions: 2.83-r0
dnsmasq
Fixed versions: 2.83-r0
dnsmasq
Fixed versions: 2.83-r0
dnsmasq
Fixed versions: 2.83-r0
Complete source record
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"modified": "2026-10-26T11:17:55.156592519Z",
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