CVE-2026-12244: CWE-190: Integer Overflow or Wraparound in NLnet Labs NSD
CVE-2026-12244 is a high-severity integer overflow vulnerability in NLnet Labs NSD version 4.14.0. When NSD is configured as a secondary server for a DNS zone, a malicious primary server can send an AXFR response containing a specially crafted SVCB resource record with an rdata size of 65512. This triggers an integer overflow in a 16-bit unsigned variable used for memory allocation, leading to a heap overflow. The vulnerability allows an attacker to perform a controlled remote code execution by overwriting up to 65509 bytes of memory.
AI Analysis
Technical Summary
The vulnerability arises from an integer overflow in NSD 4.14.0 when processing AXFR zone transfers from a primary DNS server. Specifically, a crafted SVCB RR with an rdata size of 65512 causes a uint16_t variable, which allocates space for the RR, to wrap around due to exceeding the 16-bit limit (65535). This results in a heap overflow condition that enables an attacker controlling the primary DNS server to perform a controlled remote code execution via a heap overwrite of up to 65509 bytes.
Potential Impact
An attacker with the ability to act as the primary DNS server for a zone can exploit this vulnerability to crash the NSD secondary server and execute arbitrary code remotely with the privileges of the NSD process. This can lead to full compromise of the affected system running NSD 4.14.0 as a secondary DNS server for the targeted zone.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. No official fix or patch is currently documented. Until a patch is available, avoid configuring NSD 4.14.0 as a secondary server for untrusted primary servers. Monitor vendor communications for updates and apply official fixes once released.
CVE-2026-12244: CWE-190: Integer Overflow or Wraparound in NLnet Labs NSD
Description
CVE-2026-12244 is a high-severity integer overflow vulnerability in NLnet Labs NSD version 4.14.0. When NSD is configured as a secondary server for a DNS zone, a malicious primary server can send an AXFR response containing a specially crafted SVCB resource record with an rdata size of 65512. This triggers an integer overflow in a 16-bit unsigned variable used for memory allocation, leading to a heap overflow. The vulnerability allows an attacker to perform a controlled remote code execution by overwriting up to 65509 bytes of memory.
CVSS v4.0
Score 8.7high
Affected software
Run on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The vulnerability arises from an integer overflow in NSD 4.14.0 when processing AXFR zone transfers from a primary DNS server. Specifically, a crafted SVCB RR with an rdata size of 65512 causes a uint16_t variable, which allocates space for the RR, to wrap around due to exceeding the 16-bit limit (65535). This results in a heap overflow condition that enables an attacker controlling the primary DNS server to perform a controlled remote code execution via a heap overwrite of up to 65509 bytes.
Potential Impact
An attacker with the ability to act as the primary DNS server for a zone can exploit this vulnerability to crash the NSD secondary server and execute arbitrary code remotely with the privileges of the NSD process. This can lead to full compromise of the affected system running NSD 4.14.0 as a secondary DNS server for the targeted zone.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. No official fix or patch is currently documented. Until a patch is available, avoid configuring NSD 4.14.0 as a secondary server for untrusted primary servers. Monitor vendor communications for updates and apply official fixes once released.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- NLnet Labs
- Date Reserved
- 2026-06-15T06:46:44.866Z
- Cvss Version
- 4.0
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 6a3cceac4853345fc1827806
Added to database: 06/25/2026, 06:46:04 UTC
Last enriched: 06/25/2026, 07:01:10 UTC
Last updated: 06/25/2026, 08:39:23 UTC
Views: 6
Community Reviews
0 reviewsCrowdsource mitigation strategies, share intel context, and vote on the most helpful responses. Sign in to add your voice and help keep defenders ahead.
Want to contribute mitigation steps or threat intel context? Sign in or create an account to join the community discussion.
Actions
Updates to AI analysis require Pro Console access. Upgrade inside Console → Billing.
External Links
Need more coverage?
Upgrade to Pro Console for AI refresh and higher limits.
For incident response and remediation, OffSeq services can help resolve threats faster.
Latest Threats
Check if your credentials are on the dark web
Instant breach scanning across billions of leaked records. Free tier available.