CVE-2026-82717 CNAME synthesis could lead to heap corruption
Remote attackers can trigger heap corruption in Unbound via crafted CNAME responses, potentially causing crashes or remote code execution.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-82717?
CVE-2026-82717 is a high-severity memory corruption vulnerability in Nlnetlabs Unbound, published on 16 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
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.
Weakness: CWE-122
Which versions are affected by CVE-2026-82717?
It affects 1 product.
Products include Nlnetlabs Unbound.
How do I fix CVE-2026-82717?
Upgrade to a fixed version.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-82717 being exploited?
There is no known exploitation of CVE-2026-82717 in the wild and no public exploit code.
Other vulnerabilities in Nlnetlabs Unbound
- CVE-2026-81642 Heap buffer overflow and possible Remote Code Execution when digesting DNSKEY
- CVE-2026-33278 Possible arbitrary code execution during DNSSEC validation
- CVE-2026-42944 Heap overflow with multiple NSID, COOKIE, PADDING EDNS options
- CVE-2026-42959 Crash during DNSSEC validation of malicious content
- CVE-2026-81634 Possible heap buffer overflow during DNSSEC canonicalization
Sources
Also known as ALPINE-CVE-2026-82717, AZL-101700, DEBIAN-CVE-2026-82717, ECHO-30a9-8f50-cfd9, GHSA-r5xg-xh8m-9q2w, ROOT-OS-DEBIAN-12-CVE-2026-82717 and 1 more.