CVE-2020-25687
Publication date 19 January 2021
Last updated 11 August 2025
Ubuntu priority
Description
A flaw was found in dnsmasq before version 2.83. A heap-based buffer overflow was discovered in dnsmasq when DNSSEC is enabled and before it validates the received DNS entries. This flaw allows a remote attacker, who can create valid DNS replies, to cause an overflow in a heap-allocated memory. This flaw is caused by the lack of length checks in rfc1035.c:extract_name(), which could be abused to make the code execute memcpy() with a negative size in sort_rrset() and cause a crash in dnsmasq, resulting in a denial of service. The highest threat from this vulnerability is to system availability.
Status
| Package | Ubuntu Release | Status |
|---|---|---|
| dnsmasq | 25.04 plucky |
Fixed 2.82-1ubuntu2
|
| 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 |
Not affected
|
Severity score breakdown
| Parameter | Value |
|---|---|
| Base score |
5.9 · Medium
|
| Attack vector | Network |
| Attack complexity | High |
| Privileges required | None |
| User interaction | None |
| Scope | Unchanged |
| Confidentiality | None |
| Integrity impact | None |
| Availability impact | High |
| Vector | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H |
References
Related Ubuntu Security Notices (USN)
- USN-4698-1
- Dnsmasq vulnerabilities
- 19 January 2021