Vulnerability · Published Sep 16, 2026 · Assigned by NLnet Labs
CVE-2026-82717CNAME synthesis could lead to heap corruption
High 8.4
In plain English
A high-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 0.8% (higher than 56% of all known vulnerabilities). 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 that can progressively corrupt heap memory and under certain systems and compilation options could lead to remote code execution. The vulnerability starts when CNAME synthesis during an upstream response needs to enforce(rewrite) a max TTL value in the packet buffer. Coupled with a compression pointer that points to the overwritten value and invalidates the domain name, it leads to an error path that does not properly move the buffer position and allows for the heap buffer overflow. Since this is heavily reliant on heap memory layout, results are memory corruption that eventually leads to a crash and under specific systems and compilation options remote code execution.
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-2026-82717 |
| Alpine:v3.23 | unbound | 1.25.2-r0 | ALPINE-CVE-2026-82717 |
| Alpine:v3.24 | unbound | 1.25.2-r2 | ALPINE-CVE-2026-82717 |
| Debian:12 | unbound | no fix listed | DEBIAN-CVE-2026-82717 |
| Debian:13 | unbound | 1.26.1-0+deb13u1 | DEBIAN-CVE-2026-82717 |
| Debian:14 | unbound | 1.26.1-1 | DEBIAN-CVE-2026-82717 |
| 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-2026-82717 |
| 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-2026-82717 |
| 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-2026-82717 |
| Ubuntu:26.04:LTS | unbound | 1.24.2-1ubuntu2.3 | USN-8873-1 |
| Ubuntu:26.10 | unbound | no fix listed | UBUNTU-CVE-2026-82717 |
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:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:U
References
- https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-82717.txt vendor-advisory