How severe is CVE-2026-33190?

No CVSS score has been assigned to CVE-2026-33190 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-33190?

CVE-2026-33190 affects the following packages: github.com/coredns/coredns (Go). Ecosystems affected: Go.

How do I fix CVE-2026-33190?

Update github.com/coredns/coredns to 1.14.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-33190 is resolved across your whole dependency graph.

How do I detect CVE-2026-33190 in my Go dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/coredns/coredns, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-33190 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

How does O3 Security protect against CVE-2026-33190?

O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-33190 can be triaged on real exposure rather than presence alone.

Is CVE-2026-33190 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-33190 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-33190?

CVE-2026-33190 has an EPSS (Exploit Prediction Scoring System) score of 0.5%, placing it in the 42th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-33190?

CVE-2026-33190 is classified as CWE-303 (CWE-303). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-33190 published, and has it been updated?

CVE-2026-33190 was published on May 5, 2026 and was last updated on August 12, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐹 Go

Not in CISA KEV

CVE-2026-33190 — coredns

CVE-2026-33190 is a CWE-303 vulnerability in github.com/coredns/coredns. A fix is available for github.com/coredns/coredns — see the affected versions and patch details below.

CoreDNS TSIG authentication bypass on encrypted DNS transports

Also known asGHSA-qhmp-q7xh-99rhGO-2026-5583

Published

May 5, 2026

Updated

Aug 12, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Sep 24, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

Proof-of-concept exploit code exists

CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-33190.

EPSS Exploitation Probability

via FIRST.org ↗

0.5%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs42th percentile — riskier than 42% of all scored CVEsHighest risk

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

Real-World Exposure

1 pkg affected

🐹github.com/coredns/coredns

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.

Description

Summary

CoreDNS' tsig plugin can be bypassed on non-plain-DNS transports because it trusts the transport writer's TsigStatus() instead of performing verification itself. In the attached PoC, plain DNS/TCP correctly rejects an invalid TSIG (NOTAUTH), while the same invalid-TSIG request is accepted over DoT (tls://) and DoH (https://), allowing a client without the shared secret to satisfy require all. The same bug class affects DoH3, DoQ, and gRPC.

Details

The tsig plugin decides whether an incoming TSIG was valid by consulting w.TsigStatus(): tsigStatus := w.TsigStatus(); if tsigStatus != nil { ... NOTAUTH ... } (plugin/tsig/tsig.go)

Two affected transports are shown directly in the PoC:

DoH: DoHWriter.TsigStatus() always returns nil (core/dnsserver/https.go), and the HTTP server passes unpacked DNS messages directly into the plugin chain.
DoT: the TLS server builds a dns.Server without setting TsigSecret (core/dnsserver/server_tls.go), unlike plain DNS/TCP/UDP which sets TsigSecret: s.tsigSecret (core/dnsserver/server.go).

The same transport-family bug pattern also appears on other transports:

DoH3 reuses the DoH writer path (core/dnsserver/server_https3.go -> core/dnsserver/https.go), so it inherits the same TsigStatus() == nil behavior.
DoQ uses DoQWriter.TsigStatus() error { return nil } (core/dnsserver/quic.go).
gRPC uses gRPCresponse.TsigStatus() error { return nil } (core/dnsserver/server_grpc.go).

The attached PoC was kept deliberately small (baseline TCP+DoT+DoH only) for convenience.

PoC

Adjust COREDNS_BIN in the PoC to point at right path (see the top-level const definitions for tunables as well)
Run python3 ./tsig-repro.py
Expected output: *** Start CoreDNS *** Corefile: /tmp/vh-f001-tsig-doh-dot-bypass/Corefile Log: /tmp/vh-f001-tsig-doh-dot-bypass/coredns.log

*** Baseline (plain TCP) *** no_tsig rcode=5 (expected REFUSED=5) invalid_tsig rcode=9 (expected NOTAUTH=9)

*** Candidate (DoT) *** no_tsig rcode=5 (expected REFUSED=5) invalid_tsig rcode=0 ancount=1 (expected NOERROR=0 and ancount>0)

*** Candidate (DoH) *** no_tsig http=200 rcode=5 (expected REFUSED=5) invalid_tsig http=200 rcode=0 ancount=1 (expected NOERROR=0 and ancount>0)

*** OK *** TSIG bypass reproduced: plain TCP rejects invalid TSIG, while DoT and DoH accept it. Results: /tmp/vh-f001-tsig-doh-dot-bypass/results.json

Impact

Unauthenticated remote clients can bypass TSIG-based authentication/authorization on first-class encrypted transports, enabling access to whatever the deployment intended to restrict behind tsig { require all } (e.g., zone data/privileged queries, etc.).

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐹Go	`github.com/coredns/coredns`	all versions	1.14.3`go get github.com/coredns/coredns@v1.14.3`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/coredns/coredns, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/coredns/coredns to 1.14.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-33190 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-33190 can be triaged on real exposure rather than presence alone.

Tailored to CVE-2026-33190. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

### Summary CoreDNS' tsig plugin can be bypassed on non-plain-DNS transports because it trusts the transport writer's TsigStatus() instead of performing verification itself. In the attached PoC, plain DNS/TCP correctly rejects an invalid TSIG (NOTAUTH), while the same invalid-TSIG request is accepted over DoT (tls://) and DoH (https://), allowing a client without the shared secret to satisfy require all. The same bug class affects DoH3, DoQ, and gRPC. ### Details The tsig plugin decides whether an incoming TSIG was valid by consulting w.TsigStatus(): tsigStatus := w.TsigStatus(); if tsigStatu

O3 Security · Impact-Aware SCA

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