How severe is CVE-2023-26249?

CVE-2023-26249 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2023-26249 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (49th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2023-26249?

CVE-2023-26249 affects Nic Knot Resolver. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2023-26249?

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.

When was CVE-2023-26249 published?

CVE-2023-26249 was published on 2023-02-21 and last updated on 2026-06-17.

CVE-2023-26249

CVE-2023-26249 is a high-severity vulnerability in Nic Knot Resolver with a CVSS 3.x base score of 7.5. 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-770.

Key facts

Severity: High (CVSS 3.x base score 7.5)
EPSS exploit prediction: 1% (49th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-770
Affected product: Nic Knot Resolver
Published: 2023-02-21
Last modified: 2026-06-17

Description

Knot Resolver before 5.6.0 enables attackers to consume its resources, launching amplification attacks and potentially causing a denial of service. Specifically, a single client query may lead to a hundred TCP connection attempts if a DNS server closes connections without providing a response.

Frequently asked questions

What is CVE-2023-26249?: Knot Resolver before 5.6.0 enables attackers to consume its resources, launching amplification attacks and potentially causing a denial of service. Specifically, a single client query may lead to a hundred TCP connection attempts if a DNS server closes connections without providing a response.
How severe is CVE-2023-26249?: CVE-2023-26249 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2023-26249 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (49th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2023-26249?: CVE-2023-26249 affects Nic Knot Resolver. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2023-26249?: 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.
When was CVE-2023-26249 published?: CVE-2023-26249 was published on 2023-02-21 and last updated on 2026-06-17.

References

https://www.knot-resolver.cz/2023-01-26-knot-resolver-5.6.0.html

Affected products (1)

cpe:2.3:a:nic:knot_resolver:*:*:*:*:*:*:*:*

More vulnerabilities in Nic Knot Resolver

CVE-2023-50387 — High (CVSS 7.5): Certain DNSSEC aspects of the DNS protocol (in RFC 4033, 4034, 4035, 6840, and related RFCs) allow remote attackers to…
CVE-2023-46317 — High (CVSS 7.5): Knot Resolver before 5.7.0 performs many TCP reconnections upon receiving certain nonsensical responses from servers.
CVE-2022-40188 — High (CVSS 7.5): Knot Resolver before 5.5.3 allows remote attackers to cause a denial of service (CPU consumption) because of…
CVE-2021-40083 — High (CVSS 7.5): Knot Resolver before 5.3.2 is prone to an assertion failure, triggerable by a remote attacker in an edge case (NSEC3…
CVE-2018-1110 — High (CVSS 7.5): A flaw was found in knot-resolver before version 2.3.0. Malformed DNS messages may cause denial of service.
CVE-2020-12667 — High (CVSS 7.5): Knot Resolver before 5.1.1 allows traffic amplification via a crafted DNS answer from an attacker-controlled server,…

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