Vulnerability CVE-2020-25685: Information
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.
Severity: LOW (3.7) Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
Fixed packages
Package name | Branch | Fixed in version | Version from repository | Errata ID | Task # | State |
|---|---|---|---|---|---|---|
| dnsmasq | sisyphus | 2.83-alt1 | 2.90-alt1 | ALT-PU-2021-1126-1 | 265102 | Fixed |
| dnsmasq | p10 | 2.83-alt1 | 2.90-alt1 | ALT-PU-2021-1126-1 | 265102 | Fixed |
| dnsmasq | p9 | 2.83-alt1 | 2.85-alt2.p9.1 | ALT-PU-2021-1167-1 | 265103 | Fixed |
| dnsmasq | c10f1 | 2.83-alt1 | 2.90-alt1 | ALT-PU-2021-1126-1 | 265102 | Fixed |
| dnsmasq | c9f2 | 2.83-alt1 | 2.90-alt1 | ALT-PU-2021-1217-1 | 265685 | Fixed |
References to Advisories, Solutions, and Tools
Hyperlink | Resource |
|---|---|
| https://www.jsof-tech.com/disclosures/dnspooq/ |
|
| https://bugzilla.redhat.com/show_bug.cgi?id=1889688 |
|
| GLSA-202101-17 |
|
| DSA-4844 |
|
| https://www.arista.com/en/support/advisories-notices/security-advisories/12135-security-advisory-61 |
|
| FEDORA-2021-84440e87ba | |
| FEDORA-2021-2e4c3d5a9d |