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CVE-2020-25685
Date: January 19, 2021
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.
Language: C
Severity Score
Related Resources (19)
Severity Score
Weakness Type (CWE)
CVSS v3.1
| Base Score: |
|
|---|---|
| Attack Vector (AV): | NETWORK |
| Attack Complexity (AC): | HIGH |
| Privileges Required (PR): | NONE |
| User Interaction (UI): | NONE |
| Scope (S): | UNCHANGED |
| Confidentiality (C): | NONE |
| Integrity (I): | LOW |
| Availability (A): | NONE |
CVSS v2
| Base Score: |
|
|---|---|
| Access Vector (AV): | NETWORK |
| Access Complexity (AC): | MEDIUM |
| Authentication (AU): | NONE |
| Confidentiality (C): | NONE |
| Integrity (I): | PARTIAL |
| Availability (A): | NONE |
| Additional information: |