NSD 4.14.0-4.14.2 Stack Overwrite via APL RR (adflength)
CVE-2026-12246 Published on June 25, 2026
Out of bounds stack write with crafted APL RR
NSD version 4.14.0 introduced a bug where a specially crafted APL RR, with an adflength larger than permitted for the address family will overwrite the stack when the zone is written to disk, with a maximum of 111 attacker controlled bytes.
Timeline
Issue reported by Qifan Zhang
Issue reported by Haruki Oyama
NLnet Labs shares patch with Qifan Zhang and Haruki Oyama 15 days later.
Haruki Oyama verifies patch
Qifan Zhang verifies patch 3 days later.
Issue reported by zhangph 1 day later.
NLnet Labs shares patch with zhangph
Fix released with version 4.14.3 13 days later.
Weakness Types
What is a Classic Buffer Overflow Vulnerability?
The program copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer, leading to a buffer overflow. A buffer overflow condition exists when a program attempts to put more data in a buffer than it can hold, or when a program attempts to put data in a memory area outside of the boundaries of a buffer. The simplest type of error, and the most common cause of buffer overflows, is the "classic" case in which the program copies the buffer without restricting how much is copied. Other variants exist, but the existence of a classic overflow strongly suggests that the programmer is not considering even the most basic of security protections.
CVE-2026-12246 has been classified to as a Classic Buffer Overflow vulnerability or weakness.
Improper Input Validation
The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.
Products Associated with CVE-2026-12246
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Affected Versions
NLnet Labs NSD:- Version 4.14.0 and below 4.14.3 is affected.