Description
In NLnet Labs Unbound 1.16.2 up to and including 1.25.1, a similar vulnerability as with CVE-2026-40622 in the 'ghost domain names' family of attacks was found in Unbound that could extend the ghost domain window by up to one cached TTL configured value for A/AAAA glue records. Similar to other 'ghost domain names' attacks, an adversary needs to control a (ghost) zone and be able to query a vulnerable Unbound. A single client A/AAAA query can cause Unbound to overwrite the cached expired parent-side glue rrset and essentially extend the ghost domain window by up to one cached TTL configured value ('cache-max-ttl'). In configurations where 'harden-referral-path: yes' is used (non-default configuration), no client query is required since Unbound implicitly performs that query. This is a variant of CVE-2026-40622 which only addressed the NS query.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| NLnet Labs | Unbound | 1.16.2 – < 1.25.2 | 1.25.2 |
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 | 1.25.2-1 | — |
| 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 | 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 | — |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Red Hat Hardened Images 1 | unbound +7 | 1.25.2-0.1.hum1 | RHSA-2026:43588 |
Rocky Linux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Rocky Linux 10 | unbound +6 | 1.26.1-2.el10_3 | RLSA-2026:97121 |
| Rocky Linux 9 | unbound +4 | 1.26.1-1.el9_9 | RLSA-2026:97497 |
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 15 SP7 | unbound | 1.25.2-150600.23.19.1 | SUSE-SU-2026:3885-1 |
| SLES 15 SP6 | unbound | 1.25.2-150600.23.19.1 | SUSE-SU-2026:3885-1 |
| SLES 15 SP5 | unbound | 1.25.2-150100.10.28.1 | SUSE-SU-2026:3884-1 |
| SLES 15 SP4 | unbound | 1.25.2-150100.10.28.1 | SUSE-SU-2026:3884-1 |
Show 11 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES for SAP 16.0 | unbound | 1.25.2-160000.1.1 | SUSE-SU-2026:23226-1, SUSE-SU-2026:23215-1 |
| SLES for SAP 15 SP6 | unbound | 1.25.2-150600.23.19.1 | SUSE-SU-2026:3885-1 |
| SLES for SAP 15 SP5 | unbound | 1.25.2-150100.10.28.1 | SUSE-SU-2026:3884-1 |
| SLES for SAP 15 SP4 | unbound | 1.25.2-150100.10.28.1 | SUSE-SU-2026:3884-1 |
| SLES 16.0 | unbound | 1.25.2-160000.1.1 | SUSE-SU-2026:23226-1, SUSE-SU-2026:23215-1 |
| SLE Micro 6.2 | unbound | 1.25.2-160000.1.1 | SUSE-SU-2026:23050-1 |
| SLE Micro 6.1 | unbound | 1.25.2-slfo.1.1_1.1 | SUSE-SU-2026:23349-1 |
| SLE Micro 6.0 | unbound | 1.25.2-1.1 | SUSE-SU-2026:23360-1 |
| SLE Micro 5.5 | unbound | 1.25.2-150100.10.28.1 | SUSE-SU-2026:3884-1 |
| SLE HPC 15 SP5 | unbound | 1.25.2-150100.10.28.1 | SUSE-SU-2026:3884-1 |
| SLE HPC 15 SP4 | unbound | 1.25.2-150100.10.28.1 | SUSE-SU-2026:3884-1 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Tumbleweed | unbound | 1.25.2-1.1 | openSUSE-SU-2026:11380-1 |
| openSUSE Leap 16.0 | unbound | 1.25.2-160000.1.1 | openSUSE-SU-2026:21550-1 |
Alpine
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.24 | unbound | 1.25.2-r0 | — |
| Alpine v3.23 | unbound | 1.25.2-r0 | — |
| Alpine v3.22 | unbound | 1.25.2-r0 | — |
Amazon Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Amazon Linux 2023 | unbound +5 | 1.17.1-1.amzn2023.0.13 | ALAS2023-2026-2033 |
Azure Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Azure Linux 3 | unbound | 1.25.2-1 | — |
Advisories 15
- RLSA-2026:97497 Moderate: unbound security, bug fix, and enhancement update Rocky Linux Security Advisories · Nov 13, 2026
- RLSA-2026:97121 Moderate: unbound security, bug fix, and enhancement update Rocky Linux Security Advisories · Nov 13, 2026
- WID-SEC-2026-2492 Unbound: Mehrere Schwachstellen BSI CERT-Bund (WID) · Nov 10, 2026
- RHSA-2026:43588 Red Hat Security Advisory: Red Hat Hardened Images RPMs bug fix and enhancement update Red Hat Security Advisories (RHSA) · Oct 20, 2026
- SUSE-SU-2026:3885-1 Security update for unbound SUSE / openSUSE Security Updates · Sep 10, 2026
- SUSE-SU-2026:3884-1 Security update for unbound SUSE / openSUSE Security Updates · Sep 10, 2026
- SUSE-SU-2026:23360-1 Security update for unbound SUSE / openSUSE Security Updates · Sep 10, 2026
- SUSE-SU-2026:23349-1 Security update for unbound SUSE / openSUSE Security Updates · Sep 10, 2026
- SUSE-SU-2026:23226-1 Security update for unbound SUSE / openSUSE Security Updates · Aug 27, 2026
- SUSE-SU-2026:23215-1 Security update for unbound SUSE / openSUSE Security Updates · Aug 27, 2026
- WID-SEC-2026-3038 Meinberg LANTIME: Mehrere Schwachstellen BSI CERT-Bund (WID) · Aug 26, 2026
- openSUSE-SU-2026:21550-1 Security update for unbound SUSE / openSUSE Security Updates · Aug 12, 2026
- SUSE-SU-2026:23050-1 Security update for unbound SUSE / openSUSE Security Updates · Aug 12, 2026
- ALAS2023-2026-2033 Important: unbound security update (Amazon Linux 2023) Amazon Linux Security Center (ALAS) · Aug 4, 2026
- openSUSE-SU-2026:11380-1 libunbound8-1.25.2-1.1 on GA media SUSE / openSUSE Security Updates · Jul 27, 2026
References
- https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-42955.txt vendor-advisory