Out-of-bounds write in dnsdist - CVE-2026-27853
Published: April 23, 2026
Vulnerability identifier: #VU126960
CSH Severity: Medium
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green
CVE-ID: CVE-2026-27853
CWE-ID: CWE-787
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: PowerDNS.COM B.V.
Affected software:
dnsdist
dnsdist
Detailed vulnerability description
The vulnerability allows a remote attacker to cause a denial of service.
The vulnerability exists due to an out-of-bounds write in packet rewriting via DNSQuestion:changeName or DNSResponse:changeName in custom Lua code when processing crafted DNS responses. A remote attacker can send crafted DNS responses to cause a denial of service.
The issue occurs in very specific setups using these custom Lua methods, where a rewritten packet can become larger than the initial response and exceed 65535 bytes.
How to mitigate CVE-2026-27853
Install security update from vendor's website.