CVE-2026-42959
Fixed in a distro release EPSS <1%CVSS 8.7
NLnet Labs Unbound up to and including version 1.25.0 has a denial of service vulnerability in the DNSSEC validator that can lead to a crash given malicious upstream replies. When Unbound constructs chase-reply messages for validation, the code uses the wrong counter to calculate write offsets for ADDITIONAL section rrsets. DNAME duplication could increase the ANSWER section count and authority filtering could decrease the AUTHORITY section count and create an uninitialized array slot. Combining these two, the validator later dereferences this uninitialized pointer, causing an immediate process crash. An adversary controlling a DNSSEC-signed domain can trigger this bug with a single query by configuring a DNAME chain with unsigned CNAMEs and a response containing unsigned AUTHORITY records alongside signed ADDITIONAL glue records. Unbound 1.25.1 contains a patch with a fix to use the proper counters to calculate the write offsets.
Products: NLnet Labs unbound, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9, Red Hat Hardened Images, Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 7, Red Hat OpenShift Container Platform 4
Distro releases
| Release | Package | Fixed in |
|---|---|---|
| AlmaLinux 10 | python3-unbound | 1.24.2-7.el10_2.1 |
| AlmaLinux 10 | unbound | 1.24.2-7.el10_2.1 |
| AlmaLinux 10 | unbound-anchor | 1.24.2-7.el10_2.1 |
| AlmaLinux 10 | unbound-devel | 1.24.2-7.el10_2.1 |
| AlmaLinux 10 | unbound-dracut | 1.24.2-7.el10_2.1 |
| AlmaLinux 10 | unbound-libs | 1.24.2-7.el10_2.1 |
| AlmaLinux 10 | unbound-utils | 1.24.2-7.el10_2.1 |
| AlmaLinux 8 | python3-unbound | 1.16.2-5.11.el8_10 |
| AlmaLinux 8 | unbound | 1.16.2-5.11.el8_10 |
| AlmaLinux 8 | unbound-devel | 1.16.2-5.11.el8_10 |
| AlmaLinux 8 | unbound-libs | 1.16.2-5.11.el8_10 |
| AlmaLinux 9 | python3-unbound | 1.24.2-3.el9_8.1 |
| AlmaLinux 9 | unbound | 1.24.2-3.el9_8.1 |
| AlmaLinux 9 | unbound-devel | 1.24.2-3.el9_8.1 |
| AlmaLinux 9 | unbound-dracut | 1.24.2-3.el9_8.1 |
| AlmaLinux 9 | unbound-libs | 1.24.2-3.el9_8.1 |
| Alpine 3.22 | unbound | 1.25.2-r0 |
| Alpine 3.23 | unbound | 1.25.2-r0 |
| Alpine 3.24 | unbound | 1.25.1-r0 |
| Debian 12 | unbound | no fix |
| Debian 13 | unbound | 1.22.0-2+deb13u3 |
| Debian 14 | unbound | 1.25.1-1 |
| Red Hat Enterprise Linux 10.2 | python3-unbound | 0:1.24.2-7.el10_2.1 |
| Red Hat Enterprise Linux 10.2 | python3-unbound-debuginfo | 0:1.24.2-7.el10_2.1 |
| Red Hat Enterprise Linux 10.2 | unbound | 0:1.24.2-7.el10_2.1 |
| Red Hat Enterprise Linux 10.2 | unbound-anchor | 0:1.24.2-7.el10_2.1 |
| Red Hat Enterprise Linux 10.2 | unbound-anchor-debuginfo | 0:1.24.2-7.el10_2.1 |
| Red Hat Enterprise Linux 10.2 | unbound-debuginfo | 0:1.24.2-7.el10_2.1 |
| Red Hat Enterprise Linux 10.2 | unbound-debugsource | 0:1.24.2-7.el10_2.1 |
| Red Hat Enterprise Linux 10.2 | unbound-devel | 0:1.24.2-7.el10_2.1 |
| Red Hat Enterprise Linux 10.2 | unbound-dracut | 0:1.24.2-7.el10_2.1 |
| Red Hat Enterprise Linux 10.2 | unbound-libs | 0:1.24.2-7.el10_2.1 |
| Red Hat Enterprise Linux 10.2 | unbound-libs-debuginfo | 0:1.24.2-7.el10_2.1 |
| Red Hat Enterprise Linux 10.2 | unbound-utils | 0:1.24.2-7.el10_2.1 |
| Red Hat Enterprise Linux 10.2 | unbound-utils-debuginfo | 0:1.24.2-7.el10_2.1 |
| Red Hat Enterprise Linux 8 | python3-unbound | 0:1.16.2-5.11.el8_10 |
| Red Hat Enterprise Linux 8 | python3-unbound-debuginfo | 0:1.16.2-5.11.el8_10 |
| Red Hat Enterprise Linux 8 | unbound | 0:1.16.2-5.11.el8_10 |
| Red Hat Enterprise Linux 8 | unbound-debuginfo | 0:1.16.2-5.11.el8_10 |
| Red Hat Enterprise Linux 8 | unbound-debugsource | 0:1.16.2-5.11.el8_10 |
| Red Hat Enterprise Linux 8 | unbound-devel | 0:1.16.2-5.11.el8_10 |
| Red Hat Enterprise Linux 8 | unbound-libs | 0:1.16.2-5.11.el8_10 |
| Red Hat Enterprise Linux 8 | unbound-libs-debuginfo | 0:1.16.2-5.11.el8_10 |
| Red Hat Enterprise Linux 9 | python3-unbound | 0:1.24.2-3.el9_8.1 |
| Red Hat Enterprise Linux 9 | python3-unbound-debuginfo | 0:1.24.2-3.el9_8.1 |
| Red Hat Enterprise Linux 9 | unbound | 0:1.24.2-3.el9_8.1 |
| Red Hat Enterprise Linux 9 | unbound-debuginfo | 0:1.24.2-3.el9_8.1 |
| Red Hat Enterprise Linux 9 | unbound-debugsource | 0:1.24.2-3.el9_8.1 |
| Red Hat Enterprise Linux 9 | unbound-devel | 0:1.24.2-3.el9_8.1 |
| Red Hat Enterprise Linux 9 | unbound-dracut | 0:1.24.2-3.el9_8.1 |
| Red Hat Enterprise Linux 9 | unbound-libs | 0:1.24.2-3.el9_8.1 |
| Red Hat Enterprise Linux 9 | unbound-libs-debuginfo | 0:1.24.2-3.el9_8.1 |
| Red Hat hummingbird 1 | python3-unbound | 0:1.25.1-0.1.hum1 |
| Red Hat hummingbird 1 | unbound | 0:1.25.1-0.1.hum1 |
| Red Hat hummingbird 1 | unbound-anchor | 0:1.25.1-0.1.hum1 |
| Red Hat hummingbird 1 | unbound-devel | 0:1.25.1-0.1.hum1 |
| Red Hat hummingbird 1 | unbound-dracut | 0:1.25.1-0.1.hum1 |
| Red Hat hummingbird 1 | unbound-libs | 0:1.25.1-0.1.hum1 |
| Red Hat hummingbird 1 | unbound-munin | 0:1.25.1-0.1.hum1 |
| Red Hat hummingbird 1 | unbound-utils | 0:1.25.1-0.1.hum1 |
| Rocky Linux 10 | unbound | 0:1.24.2-7.el10_2.1 |
| Rocky Linux 8 | unbound | 0:1.16.2-5.11.el8_10 |
| Rocky Linux 9 | unbound | 0:1.24.2-3.el9_8.1 |
| SUSE Linux Enterprise High Performance Computing 15 SP4-ESPOS | unbound | 1.20.0-150100.10.25.1 |
| SUSE Linux Enterprise High Performance Computing 15 SP4-LTSS | unbound | 1.20.0-150100.10.25.1 |
| SUSE Linux Enterprise High Performance Computing 15 SP5-ESPOS | unbound | 1.20.0-150100.10.25.1 |
| SUSE Linux Enterprise High Performance Computing 15 SP5-LTSS | unbound | 1.20.0-150100.10.25.1 |
| SUSE Linux Enterprise Micro 5.5 | unbound | 1.20.0-150100.10.25.1 |
| SUSE Linux Enterprise Server 15 SP4-LTSS | unbound | 1.20.0-150100.10.25.1 |
| SUSE Linux Enterprise Server 15 SP5-LTSS | unbound | 1.20.0-150100.10.25.1 |
| SUSE Linux Enterprise Server 16.0 | unbound | 1.24.1-160000.2.1 |
| SUSE Linux Enterprise Server for SAP Applications 15 SP4 | unbound | 1.20.0-150100.10.25.1 |
| SUSE Linux Enterprise Server for SAP Applications 15 SP5 | unbound | 1.20.0-150100.10.25.1 |
| SUSE Linux Enterprise Server for SAP applications 16.0 | unbound | 1.24.1-160000.2.1 |
| SUSE Linux Micro 6.2 | unbound | 1.24.1-160000.2.1 |
| Ubuntu 22.04 LTS | unbound | 1.13.1-1ubuntu5.15 |
| Ubuntu 24.04 LTS | unbound | 1.19.2-1ubuntu3.8 |
| Ubuntu 25.10 | unbound | 1.22.0-2ubuntu2.3 |
| Ubuntu 26.04 LTS | unbound | 1.24.2-1ubuntu2.1 |
| Ubuntu Pro 14.04 LTS | unbound | 1.4.22-1ubuntu4.14.04.3+esm3 |
| Ubuntu Pro 16.04 LTS | unbound | 1.5.8-1ubuntu1.1+esm3 |
| Ubuntu Pro 18.04 LTS | unbound | 1.6.7-1ubuntu2.6+esm4 |
| Ubuntu Pro 20.04 LTS | unbound | 1.9.4-2ubuntu1.11+esm1 |
| openSUSE Leap 16.0 | unbound | 1.24.1-160000.2.1 |
| openSUSE Tumbleweed | unbound | 1.25.1-1.1 |