CVE-2020-25685
Publication date 19 January 2021
Last updated 24 July 2024
Ubuntu priority
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.
Status
| Package | Ubuntu Release | Status |
|---|---|---|
| dnsmasq | 24.04 LTS noble |
Fixed 2.82-1ubuntu2
|
| 22.04 LTS jammy |
Fixed 2.82-1ubuntu2
|
|
| 20.04 LTS focal |
Fixed 2.80-1.1ubuntu1.2
|
|
| 18.04 LTS bionic |
Fixed 2.79-1ubuntu0.2
|
|
| 16.04 LTS xenial |
Fixed 2.75-1ubuntu0.16.04.7
|
|
| 14.04 LTS trusty |
Needs evaluation
|
Severity score breakdown
| Parameter | Value |
|---|---|
| Base score |
3.7 · Low
|
| Attack vector | Network |
| Attack complexity | High |
| Privileges required | None |
| User interaction | None |
| Scope | Unchanged |
| Confidentiality | None |
| Integrity impact | Low |
| Availability impact | None |
| Vector | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N |
References
Related Ubuntu Security Notices (USN)
- USN-4698-1
- Dnsmasq vulnerabilities
- 19 January 2021