Vulnerability · Published Sep 16, 2026 · Assigned by NLnet Labs
CVE-2026-81642Heap buffer overflow and possible Remote Code Execution when digesting DNSKEY
Critical 9.1
In plain English
A critical-severity heap buffer overflow in Unbound from NLnet Labs. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 1.0% (higher than 62% of all known vulnerabilities). Ready-made attack tooling exists: public proof-of-concept code. Fixed versions are available - upgrade the affected package.
Official description
In NLnet Labs Unbound up to and including 1.26.0, a vulnerability was found in the DNSSEC validator that enables denial of service and possible remote code execution as a result of digesting DNSKEYs. A DNSKEY with an owner compression pointer to its own RDATA can overflow the digest buffer. Remote code execution is possible through attacker controlled data. An adversary can exploit the vulnerability by controlling a malicious zone and querying a vulnerable Unbound.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| AlmaLinux:10 | python3-unbound | 1.24.2-7.el10_2.6 | ALSA-2026:71419 |
| AlmaLinux:8 | python3-unbound | 1.16.2-5.14.el8_10.4 | ALSA-2026:70754 |
| AlmaLinux:9 | python3-unbound | 1.24.2-3.el9_8.8 | ALSA-2026:71487 |
| AlmaLinux:10 | unbound | 1.24.2-7.el10_2.6 | ALSA-2026:71419 |
| AlmaLinux:8 | unbound | 1.16.2-5.14.el8_10.4 | ALSA-2026:70754 |
| AlmaLinux:9 | unbound | 1.24.2-3.el9_8.8 | ALSA-2026:71487 |
| AlmaLinux:10 | unbound-anchor | 1.24.2-7.el10_2.6 | ALSA-2026:71419 |
| AlmaLinux:10 | unbound-devel | 1.24.2-7.el10_2.6 | ALSA-2026:71419 |
| AlmaLinux:8 | unbound-devel | 1.16.2-5.14.el8_10.4 | ALSA-2026:70754 |
| AlmaLinux:9 | unbound-devel | 1.24.2-3.el9_8.8 | ALSA-2026:71487 |
| AlmaLinux:10 | unbound-dracut | 1.24.2-7.el10_2.6 | ALSA-2026:71419 |
| AlmaLinux:9 | unbound-dracut | 1.24.2-3.el9_8.8 | ALSA-2026:71487 |
| AlmaLinux:10 | unbound-libs | 1.24.2-7.el10_2.6 | ALSA-2026:71419 |
| AlmaLinux:8 | unbound-libs | 1.16.2-5.14.el8_10.4 | ALSA-2026:70754 |
| AlmaLinux:9 | unbound-libs | 1.24.2-3.el9_8.8 | ALSA-2026:71487 |
| AlmaLinux:10 | unbound-utils | 1.24.2-7.el10_2.6 | ALSA-2026:71419 |
| Alpine:v3.22 | unbound | 1.25.2-r0 | ALPINE-CVE-2026-81642 |
| Alpine:v3.23 | unbound | 1.25.2-r0 | ALPINE-CVE-2026-81642 |
| Alpine:v3.24 | unbound | 1.25.2-r2 | ALPINE-CVE-2026-81642 |
| Debian:12 | unbound | no fix listed | DEBIAN-CVE-2026-81642 |
| Debian:13 | unbound | 1.26.1-0+deb13u1 | DEBIAN-CVE-2026-81642 |
| Debian:14 | unbound | 1.26.1-1 | DEBIAN-CVE-2026-81642 |
| Rocky Linux:10 | unbound | 0:1.24.2-7.el10_2.6 | RLSA-2026:71419 |
| Rocky Linux:8 | unbound | 0:1.16.2-5.14.el8_10.4 | RLSA-2026:70754 |
| Rocky Linux:9 | unbound | 0:1.24.2-3.el9_8.8 | RLSA-2026:71487 |
| Ubuntu:22.04:LTS | unbound | 1.13.1-1ubuntu5.16 | UBUNTU-CVE-2026-81642 |
| Ubuntu:22.04:LTS | unbound | 1.13.1-1ubuntu5.16 | USN-8873-1 |
| Ubuntu:24.04:LTS | unbound | 1.19.2-1ubuntu3.10 | UBUNTU-CVE-2026-81642 |
| Ubuntu:24.04:LTS | unbound | 1.19.2-1ubuntu3.10 | USN-8873-1 |
| Ubuntu:26.04:LTS | unbound | 1.24.2-1ubuntu2.3 | UBUNTU-CVE-2026-81642 |
| Ubuntu:26.04:LTS | unbound | 1.24.2-1ubuntu2.3 | USN-8873-1 |
| Ubuntu:26.10 | unbound | no fix listed | UBUNTU-CVE-2026-81642 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| NLnet Labs | Unbound | 0 – before 1.26.1 |
Weakness: CWE-122 · Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:U/U:Red
References
- https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-81642.txt vendor-advisory