CVE-2026-27853 Out-of-bounds write when rewriting large DNS packets

Medium 5.9 Published 31 Mar 2026 Updated 31 Mar 2026

Attackers can cause a denial of service in DNSdist by triggering an out-of-bounds write via crafted DNS responses processed by custom Lua scripts.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Over the internet
Victim action needed: Not needed
Fix: Available

What is CVE-2026-27853?

CVE-2026-27853 is a medium-severity memory corruption vulnerability in PowerDNS DNSdist, published on 31 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

An attacker might be able to trigger an out-of-bounds write by sending crafted DNS responses to a DNSdist using the DNSQuestion:changeName or DNSResponse:changeName methods in custom Lua code. In some cases the rewritten packet might become larger than the initial response and even exceed 65535 bytes, potentially leading to a crash resulting in denial of service.

Weakness: CWE-787

Which versions are affected by CVE-2026-27853?

It affects 1 product.

Products include Powerdns Dnsdist.

How do I fix CVE-2026-27853?

Apply the vendor's patch.

Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.

Is CVE-2026-27853 being exploited?

There is no known exploitation of CVE-2026-27853 in the wild and no public exploit code.

Sources

Also known as DEBIAN-CVE-2026-27853, GHSA-w68q-j3pw-29rg, UBUNTU-CVE-2026-27853.