Description
In NLnetLabs Unbound up to and including 1.26.0, a degradation of service vulnerability is present in the TCP/DoT reading procedure where there is no limit on consecutive reads. A malicious actor that can stream and sustain a rate of distinct uncached names over the TCP/DoT connection, monopolizes a single worker's entire event loop for as long as its writes stay ahead of the drain.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| NLnet Labs | Unbound | < 1.26.1 | 1.26.1 |
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 | 1.26.1-1 | — |
| Debian 13 | unbound | 1.26.1-0+deb13u1 | — |
| Debian 12 | unbound | No fix yet | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 26.10 | unbound | 1.25.1-1ubuntu3.1 | USN-8946-2 |
| Ubuntu 26.04 LTS | unbound | 1.24.2-1ubuntu2.4 | USN-8946-1 |
| Ubuntu 24.04 LTS | unbound | 1.19.2-1ubuntu3.12 | USN-8946-1 |
| Ubuntu 22.04 LTS | unbound | 1.13.1-1ubuntu5.17 | USN-8946-1 |
Show 4 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Pro 20.04 LTS | unbound | 1.9.4-2ubuntu1.11+esm3 | USN-8946-1 |
| Ubuntu Pro 18.04 LTS | unbound | 1.6.7-1ubuntu2.6+esm6 | USN-8946-1 |
| Ubuntu Pro 16.04 LTS | unbound | 1.5.8-1ubuntu1.1+esm5 | USN-8946-1 |
| Ubuntu Pro 14.04 LTS | unbound | 1.4.22-1ubuntu4.14.04.3+esm5 | USN-8946-1 |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Red Hat Hardened Images 1 | unbound +7 | 1.26.1-1.hum1 | RHSA-2026:68590 |
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 15 SP7 | unbound | 1.26.1-150600.23.24.1 | SUSE-SU-2026:4620-1 |
| SLES 15 SP6 | unbound | 1.26.1-150600.23.24.1 | SUSE-SU-2026:4620-1 |
| SLES 15 SP5 | unbound | 1.26.1-150100.10.31.1 | SUSE-SU-2026:4624-1 |
| SLES 15 SP4 | unbound | 1.26.1-150100.10.31.1 | SUSE-SU-2026:4624-1 |
Show 11 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES for SAP 16.0 | unbound | 1.26.1-160000.1.1 | SUSE-SU-2026:24226-1 |
| SLES for SAP 15 SP6 | unbound | 1.26.1-150600.23.24.1 | SUSE-SU-2026:4620-1 |
| SLES for SAP 15 SP5 | unbound | 1.26.1-150100.10.31.1 | SUSE-SU-2026:4624-1 |
| SLES for SAP 15 SP4 | unbound | 1.26.1-150100.10.31.1 | SUSE-SU-2026:4624-1 |
| SLES 16.0 | unbound | 1.26.1-160000.1.1 | SUSE-SU-2026:24226-1 |
| SLE Micro 6.2 | unbound | 1.26.1-160000.1.1 | SUSE-SU-2026:24128-1 |
| SLE Micro 6.1 | unbound | 1.26.1-slfo.1.1_1.1 | SUSE-SU-2026:24376-1 |
| SLE Micro 6.0 | unbound | 1.26.1-159998.1.1 | SUSE-SU-2026:24135-1 |
| SLE Micro 5.5 | unbound | 1.26.1-150100.10.31.1 | SUSE-SU-2026:4624-1 |
| SLE HPC 15 SP5 | unbound | 1.26.1-150100.10.31.1 | SUSE-SU-2026:4624-1 |
| SLE HPC 15 SP4 | unbound | 1.26.1-150100.10.31.1 | SUSE-SU-2026:4624-1 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Tumbleweed | unbound | 1.26.1-1.1 | openSUSE-SU-2026:11930-1 |
| openSUSE Leap 16.0 | unbound | 1.26.1-160000.1.1 | openSUSE-SU-2026:22082-1 |
Amazon Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Amazon Linux 2023 | unbound +5 | 1.17.1-1.amzn2023.0.15 | ALAS2023-2026-3127 |
Azure Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Azure Linux 3 | unbound | 1.26.1-1 | — |
Advisories 13
- USN-8946-2 unbound vulnerabilities Ubuntu Security Notices (USN) · Nov 11, 2026
- WID-SEC-2026-3392 Unbound: Mehrere Schwachstellen BSI CERT-Bund (WID) · Nov 10, 2026
- SUSE-SU-2026:24376-1 Security update for unbound SUSE / openSUSE Security Updates · Oct 27, 2026
- USN-8946-1 unbound vulnerabilities Ubuntu Security Notices (USN) · Oct 21, 2026
- SUSE-SU-2026:24226-1 Security update for unbound SUSE / openSUSE Security Updates · Oct 21, 2026
- openSUSE-SU-2026:22082-1 Security update for unbound SUSE / openSUSE Security Updates · Oct 19, 2026
- RHSA-2026:68590 Red Hat Security Advisory: Red Hat Hardened Images RPMs bug fix and enhancement update Red Hat Security Advisories (RHSA) · Oct 17, 2026
- SUSE-SU-2026:24135-1 Security update for unbound SUSE / openSUSE Security Updates · Oct 15, 2026
- SUSE-SU-2026:24128-1 Security update for unbound SUSE / openSUSE Security Updates · Oct 13, 2026
- SUSE-SU-2026:4620-1 Security update for unbound SUSE / openSUSE Security Updates · Oct 13, 2026
- SUSE-SU-2026:4624-1 Security update for unbound SUSE / openSUSE Security Updates · Oct 13, 2026
- openSUSE-SU-2026:11930-1 libunbound8-1.26.1-1.1 on GA media SUSE / openSUSE Security Updates · Sep 30, 2026
- ALAS2023-2026-3127 Important: unbound security update (Amazon Linux 2023) Amazon Linux Security Center (ALAS) · Sep 28, 2026
References
- https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-80225.txt vendor-advisory