Stack-based buffer overflow in NSD - CVE-2026-12246
Published: June 25, 2026
Vulnerability identifier: #VU135156
CSH Severity: Medium
CVSS v4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-12246
CWE-ID: CWE-121
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote user to execute arbitrary code.
The vulnerability exists due to a stack-based buffer overflow in the APL RR rdata handling logic when writing a zonefile to disk. A remote user can provide a specially crafted APL resource record with an oversized adflength value to execute arbitrary code.
Exploitation requires control of data from a configured primary in a multi-tenant secondary DNS deployment.
Affected software
NSD
Fedora
Ubuntu
nsd (Ubuntu package)
nsd
Fedora
Ubuntu
nsd (Ubuntu package)
nsd
How to mitigate CVE-2026-12246
Install security update from vendor's website.
NSD - update to 4.14.3
nsd (Ubuntu package) - addressed in versions 4.1.7-1ubuntu0.1~esm1, 4.1.17-1ubuntu0.1~esm1, 4.1.26-1ubuntu0.1~esm1, 4.3.9-1ubuntu0.1~esm1, 4.8.0-1ubuntu0.1~esm1, 4.14.0-1ubuntu0.1~esm1
nsd - addressed in versions 4.14.3-1.fc43, 4.14.3-1.fc44, 4.15.0-1.el10_3
nsd (Ubuntu package) - addressed in versions 4.1.7-1ubuntu0.1~esm1, 4.1.17-1ubuntu0.1~esm1, 4.1.26-1ubuntu0.1~esm1, 4.3.9-1ubuntu0.1~esm1, 4.8.0-1ubuntu0.1~esm1, 4.14.0-1ubuntu0.1~esm1
nsd - addressed in versions 4.14.3-1.fc43, 4.14.3-1.fc44, 4.15.0-1.el10_3