Description
NLnet Labs Unbound up to and including version 1.26.1 limits compression-pointer traversal for each individual domain-name operation but has no aggregate inbound decompression-work budget. Many chained compression pointers in a message results in a lot of CPU usage following them. A malicious actor with recursive-query access and control of an ordinarily delegated authority that serves specially crafted replies can exploit the vulnerability and degrade Unbound's general performance.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| NLnet Labs | Unbound | < 1.26.2 | 1.26.2 |
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 | unbound | 1.26.2-1 | — |
| Debian 13 | unbound | 1.26.2-0+deb13u1 | — |
| Debian 12 | unbound | No fix yet | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 26.10 | unbound | No fix yet | — |
| Ubuntu 26.04 LTS | unbound | No fix yet | — |
| Ubuntu 24.04 LTS | unbound | No fix yet | — |
| Ubuntu 22.04 LTS | unbound | No fix yet | — |
Show 4 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Pro 20.04 LTS | unbound | No fix yet | — |
| Ubuntu Pro 18.04 LTS | unbound | No fix yet | — |
| Ubuntu Pro 16.04 LTS | unbound | No fix yet | — |
| Ubuntu Pro 14.04 LTS | unbound | No fix yet | — |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Tumbleweed | unbound | 1.26.2-1.1 | openSUSE-SU-2026:12257-1 |
Amazon Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Amazon Linux 2023 | unbound +5 | 1.17.1-1.amzn2023.0.17 | ALAS2023-2026-3313 |
Azure Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Azure Linux 3 | unbound | 1.26.2-1 | — |
Advisories 3
- WID-SEC-2026-4073 Unbound: Mehrere Schwachstellen BSI CERT-Bund (WID) · Nov 9, 2026
- ALAS2023-2026-3313 Moderate: unbound security update (Amazon Linux 2023) Amazon Linux Security Center (ALAS) · Oct 26, 2026
- openSUSE-SU-2026:12257-1 libunbound8-1.26.2-1.1 on GA media SUSE / openSUSE Security Updates · Oct 24, 2026
References
- https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-96405.txt vendor-advisory