CVE-2026-33190: coredns — Exploit & Fix

Description

CoreDNS is a DNS server that chains plugins. In versions prior to 1.14.3, the tsig plugin can be bypassed on non-plain-DNS transports (DoT, DoH, DoH3, DoQ, and gRPC) because it trusts the transport writer's TsigStatus() instead of performing verification itself. The DoH and DoH3 writer's TsigStatus() always returns nil, the DoT server does not set TsigSecret on the dns.Server, and the DoQ and gRPC writers also unconditionally return nil. This allows an unauthenticated remote client to bypass TSIG-based authentication and access resources intended to be restricted behind a tsig require all policy. Plain DNS over TCP and UDP are not affected. This issue has been fixed in version 1.14.3.

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CVSS v3.1 Score

7.5

HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

EPSS — Exploit Prediction

0.0008

Probability of exploitation

0.23%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-303 CWE-303

Affected Products

Vendor	Product	Versions
coredns.io	coredns	< 1.14.3

References

Advisories & Patches

https://github.com/coredns/coredns/security/advisories/GHSA-qhmp-q7xh-99rh https://github.com/coredns/coredns/security/advisories/GHSA-qhmp-q7xh-99rh

Exploits

https://github.com/coredns/coredns/security/advisories/GHSA-qhmp-q7xh-99rh https://github.com/coredns/coredns/security/advisories/GHSA-qhmp-q7xh-99rh

Other References

https://github.com/coredns/coredns/releases/tag/v1.14.3

Frequently Asked Questions

What is CVE-2026-33190? +

CoreDNS is a DNS server that chains plugins. In versions prior to 1.14.3, the tsig plugin can be bypassed on non-plain-DNS transports (DoT, DoH, DoH3, DoQ, and gRPC) because it trusts the transport writer's TsigStatus() instead of performing verification itself. The DoH and DoH3 writer's TsigStatus() always returns nil, the DoT server does not set TsigSecret on the dns.Server, and the DoQ and gRPC writers also unconditionally return nil. This allows an unauthenticated remote client to bypass TSIG-based authentication and access resources intended to be restricted behind a tsig require all policy. Plain DNS over TCP and UDP are not affected. This issue has been fixed in version 1.14.3. It has a CVSS v3.1 base score of 7.5 (HIGH).

How severe is CVE-2026-33190? +

CVE-2026-33190 has a CVSS v3.1 score of 7.5 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0008, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-33190? +

CVE-2026-33190 affects products from coredns.io, specifically: coredns. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-33190? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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