How severe is CVE-2025-47950?

CVE-2025-47950 has a CVSS score of 7.5/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2025-47950?

CVE-2025-47950 affects the following packages: github.com/coredns/coredns (Go). Ecosystems affected: Go.

How do I fix CVE-2025-47950?

Update github.com/coredns/coredns to 1.12.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-47950 is resolved across your whole dependency graph.

How do I detect CVE-2025-47950 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-2025-47950 if there is no patch (or I can't update yet)?

Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Is CVE-2025-47950 actively exploited in the wild?

No public exploit code has been indexed for CVE-2025-47950 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-2025-47950?

CVE-2025-47950 has an EPSS (Exploit Prediction Scoring System) score of 1.2%, placing it in the 68th 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-2025-47950?

CVE-2025-47950 is classified as CWE-770 (CWE-770). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2025-47950 published, and has it been updated?

CVE-2025-47950 was published on June 6, 2025 and was last updated on October 28, 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

HIGH severity

CVE-2025-47950 — coredns

HIGHFix: coredns/coredns@efaed02

CVE-2025-47950 is a high-severity (CVSS 7.5) CWE-770 vulnerability in github.com/coredns/coredns. A fix is available for github.com/coredns/coredns — see the affected versions and patch details below.

CoreDNS Vulnerable to DoQ Memory Exhaustion via Stream Amplification

Also known asGHSA-cvx7-x8pj-x2gwGO-2025-3743

Published

Jun 6, 2025

Updated

Oct 28, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 2, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2025-47950.

EPSS Exploitation Probability

via FIRST.org ↗

1.2%probability of exploitation in next 30 days

Lower Risk+0.01%

Lower risk than most CVEs68th percentile — riskier than 68% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

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

A Denial of Service (DoS) vulnerability was discovered in the CoreDNS DNS-over-QUIC (DoQ) server implementation. The server previously created a new goroutine for every incoming QUIC stream without imposing any limits on the number of concurrent streams or goroutines. A remote, unauthenticated attacker could open a large number of streams, leading to uncontrolled memory consumption and eventually causing an Out Of Memory (OOM) crash — especially in containerized or memory-constrained environments.

Impact

Component: server_quic.go
Attack Vector: Remote, network-based
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Impact: High availability loss (OOM kill or unresponsiveness)

This issue affects deployments with quic:// enabled in the Corefile. A single attacker can cause the CoreDNS instance to become unresponsive using minimal bandwidth and CPU.

Patches

The patch introduces two key mitigation mechanisms:

max_streams: Caps the number of concurrent QUIC streams per connection. Default: 256.
worker_pool_size: Introduces a server-wide, bounded worker pool to process incoming streams. Default: 1024.

This eliminates the 1:1 stream-to-goroutine model and ensures that CoreDNS remains resilient under high concurrency. The new configuration options are exposed through the quic Corefile block:

quic {
    max_streams 256
    worker_pool_size 1024
}

These defaults are generous and aligned with typical DNS-over-QUIC client behavior.

Workarounds

If you're unable to upgrade immediately, you can:

Disable QUIC support by removing or commenting out the quic:// block in your Corefile
Use container runtime resource limits to detect and isolate excessive memory usage
Monitor QUIC connection patterns and alert on anomalies

References

Credit

Thanks to @thevilledev for disclovering this vulnerability and contributing a high-quality fix.

For more information

Please consult our security guide for more information regarding our security process.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐹Go	`github.com/coredns/coredns`	all versions	1.12.2`go get github.com/coredns/coredns@v1.12.2`

Affected Products

1 product · 1 configurations

Application

corednscoredns.io

< 1.12.2

range

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 1.12.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-47950 is resolved across your whole dependency graph.
Workarounds
Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatModerate

On a Red Hat system, a denial of service to the CoreDNS service will not take down the host system, so the availability impact is assessed as Low for Red Hat systems.

Workaround published by Red Hat

Users unable to upgrade should manually disable the QUIC protocol support.

Source: Red Hat security advisory for CVE-2025-47950 (CC BY 4.0)

Product	Fixed in	Advisory
Red Hat Advanced Cluster Management for Kubernetes 2.13	`rhacm2/lighthouse-coredns-rhel9:v0.20.2-1759168533`	RHSA-2025:17128
Red Hat Advanced Cluster Management for Kubernetes 2.13	`rhacm2/lighthouse-agent-rhel9:1782924920`	RHSA-2026:36873
Red Hat Advanced Cluster Management for Kubernetes 2.14	`rhacm2/lighthouse-agent-rhel9:v0.21-1762794425`	RHSA-2025:21892

Frequently Asked Questions

### Summary A **Denial of Service (DoS)** vulnerability was discovered in the CoreDNS DNS-over-QUIC (DoQ) server implementation. The server previously created a new goroutine for every incoming QUIC stream without imposing any limits on the number of concurrent streams or goroutines. A remote, unauthenticated attacker could open a large number of streams, leading to uncontrolled memory consumption and eventually causing an Out Of Memory (OOM) crash — especially in containerized or memory-constrained environments. ### Impact - **Component**: `server_quic.go` - **Attack Vector**: Remote, netw