How severe is CVE-2026-12244?

CVE-2026-12244 has a CVSS 3.x base score of 8.8, rated high severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2026-12244 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (22nd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-12244?

CVE-2026-12244 affects Nlnetlabs Nsd. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-12244?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

Does CVE-2026-12244 have an EU (EUVD) identifier?

Yes. CVE-2026-12244 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-39182.

When was CVE-2026-12244 published?

CVE-2026-12244 was published on 2026-06-25 and last updated on 2026-06-26.

CVE-2026-12244

CVE-2026-12244 is a high-severity vulnerability in Nlnetlabs Nsd with a CVSS 3.x base score of 8.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-122.

Key facts

Severity: High (CVSS 3.x base score 8.8)
CVSS v4: 8.7
EPSS exploit prediction: 0% (22nd percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-39182
Weakness: CWE-122
Affected product: Nlnetlabs Nsd
Published: 2026-06-25
Last modified: 2026-06-26

Description

If NSD is configured as secondary for a zone, the primary of that zone can crash NSD with an AXFR containing a DNS message with a special crafted SVCB RR with an rdata size of 65512, that let's an (uint16_t) variable that is used to allocate space needed for the RR wrap (because total size > 65535), causing a heap overflow. The attacker can perform a controlled (RCE class) head write of up to 65509 bytes

Frequently asked questions

What is CVE-2026-12244?: If NSD is configured as secondary for a zone, the primary of that zone can crash NSD with an AXFR containing a DNS message with a special crafted SVCB RR with an rdata size of 65512, that let's an (uint16_t) variable that is used to allocate space needed for the RR wrap (because total size > 65535), causing a heap overflow. The attacker can perform a controlled (RCE class) head write of up to 65509 bytes
How severe is CVE-2026-12244?: CVE-2026-12244 has a CVSS 3.x base score of 8.8, rated high severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2026-12244 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (22nd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-12244?: CVE-2026-12244 affects Nlnetlabs Nsd. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-12244?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2026-12244 have an EU (EUVD) identifier?: Yes. CVE-2026-12244 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-39182.
When was CVE-2026-12244 published?: CVE-2026-12244 was published on 2026-06-25 and last updated on 2026-06-26.

References

https://www.nlnetlabs.nl/downloads/nsd/CVE-2026-12244.txt

Affected products (1)

cpe:2.3:a:nlnetlabs:nsd:*:*:*:*:*:*:*:*

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