Description
Knot Resolver before 5.5.3 allows remote attackers to cause a denial of service (CPU consumption) because of algorithmic complexity. During an attack, an authoritative server must return large NS sets or address sets.
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | knot-resolver | 5.5.3-1 | — |
| Debian 13 | knot-resolver | 5.5.3-1 | — |
| Debian 12 | knot-resolver | 5.5.3-1 | — |
| Debian 10 | knot-resolver | 3.2.1-3+deb10u1 | DLA-3139-1 |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 20.04 LTS | knot-resolver | 3.2.1-3ubuntu2.1 | USN-6225-1 |
Show 3 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Pro 22.04 LTS | knot-resolver | 5.4.4-1ubuntu0.1~esm1 | USN-6225-1 |
| Ubuntu Pro 18.04 LTS | knot-resolver | 2.1.1-1ubuntu0.1~esm2 | USN-6225-1 |
| Ubuntu Pro 16.04 LTS | knot-resolver | 1.0.0~beta3-1ubuntu0.1~esm1 | USN-6225-1 |
Alpine
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.24 | knot-resolver | 5.5.3-r0 | — |
| Alpine v3.23 | knot-resolver | 5.5.3-r0 | — |
| Alpine v3.22 | knot-resolver | 5.5.3-r0 | — |
| Alpine v3.21 | knot-resolver | 5.5.3-r0 | — |
| Alpine v3.20 | knot-resolver | 5.5.3-r0 | — |
Show 4 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.19 | knot-resolver | 5.5.3-r0 | — |
| Alpine v3.18 | knot-resolver | 5.5.3-r0 | — |
| Alpine v3.17 | knot-resolver | 5.5.3-r0 | — |
| Alpine v3.16 | knot-resolver | 5.5.3-r0 | — |
Advisories 2
- USN-6225-1 knot-resolver vulnerability Ubuntu Security Notices (USN) · Jun 25, 2026
- DLA-3139-1 knot-resolver - security update Debian Security (DSA / DLA) · Mar 9, 2026
References
- https://gitlab.nic.cz/knot/knot-resolver/-/merge_requests/1343#note_262558
- FEDORA-2022-68ad89b21c vendor-advisory
- FEDORA-2022-357cc1a81b vendor-advisory
- FEDORA-2022-2a4ca7b18d vendor-advisory
- [debian-lts-announce] 20221008 [SECURITY] [DLA 3139-1] knot-resolver security update mailing-list