Description
Novel vulnerabilities to launch algorithmic complexity attacks on DNSSEC have been researched under the term 'ReTrap'. These result in degradation of service when malicious zones are used to serve the algorithmic complexity vulnerabilities. NLnet Labs Unbound up to and including 1.26.0 is vulnerable to some of them. TagTrap, where the triple(Zone, Algo, KeyTag) matching mechanism introduces a significant attack vector when resolvers handle malicious responses containing numerous mismatched DNSKEY, RRSIG, and DS record. DelegationTrap, where constructing the chain-of-trust requires iterative validation of DNSKEY and DS records from the root zone downward. For deeply nested domains, this results in significant computational overhead. NsecTrap, where responses with excessive invalid NSEC records compel the resolver to validate each one. AdditionalTrap, where Unbound by default would try to DNSSEC validate the ADDITIONAL section as well. This can be exploited to waste validation resources by malicious users.
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 |
| Amazon Linux 2 | unbound +4 | 1.7.3-15.amzn2.0.17 | ALAS2-2026-3941 |
Azure Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Azure Linux 3 | unbound | 1.26.1-1 | — |
Advisories 14
- 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
- ALAS2-2026-3941 Important: unbound security update (Amazon Linux 2) Amazon Linux Security Center (ALAS) · Sep 28, 2026
References
- https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-85501.txt vendor-advisory