CVE-2026-33413: etcd: Authorization bypasses in multiple APIs
Impact What kind of vulnerability is it? Who is impacted?
Multiple vulnerabilities allow unauthorized users to bypass authentication or authorization checks and call certain etcd functions in clusters that expose the gRPC API to untrusted or partially trusted clients.
In unpatched etcd clusters with etcd auth enabled, unauthorized users are able to:
- call MemberList and learn cluster topology, including member IDs and advertised endpoints - call Alarm, which can be abused for operational disruption or denial of service - use Lease APIs, interfering with TTL-based keys and lease ownership - trigger compaction, permanently removing historical revisions and disrupting watch, audit, and recovery workflows
Kubernetes does not rely on etcd’s built-in authentication and authorization. Instead, the API server handles authentication and authorization itself, so typical Kubernetes deployments are not affected.
Patches Has the problem been patched? What versions should users upgrade to?
These vulnerabilities are patched in the following versions:
etcd 3.6.9 etcd 3.5.28 etcd 3.4.42
Workarounds Is there a way for users to fix or remediate the vulnerability without upgrading?
If upgrading is not immediately possible, reduce exposure by treating the affected RPCs as unauthenticated in practice.
- restrict network access to etcd server ports so only trusted components can connect - require strong client identity at the transport layer, such as mTLS with tightly scoped client certificate distribution
Reporters Community efforts help keep etcd secure
The etcd community thanks Isaac David, bugbunny.ai, Asim Viladi Oglu Manizada, Alex Schapiro & Ahmed Allam from Strix security, Luke Francis, and @OLU-DEVX for reporting these vulnerabilities.
Dependency Between Reported Issues
These issues all originate from the same underlying flaw in the gRPC API layer.
They affect the same API surface and share a common root cause. In practice, the fix is implemented as a single, unified change at the API layer, which resolves all issues together.
Given this, we believe these issues are best treated as a single vulnerability and should be assigned a single CVE.
Other sources
etcd is a distributed key-value store for the data of a distributed system. Prior to versions 3.4.42, 3.5.28, and 3.6.9, unauthorized users may bypass authentication or authorization checks and call certain etcd functions in clusters that expose the gRPC API to untrusted or partially trusted clients. In unpatched etcd clusters with etcd auth enabled, unauthorized users are able to call MemberList and learn cluster topology, including member IDs and advertised endpoints; call Alarm, which can be abused for operational disruption or denial of service; use Lease APIs, interfering with TTL-based keys and lease ownership; and/or trigger compaction, permanently removing historical revisions and disrupting watch, audit, and recovery workflows. Kubernetes does not rely on etcd’s built-in authentication and authorization. Instead, the API server handles authentication and authorization itself, so typical Kubernetes deployments are not affected. Versions 3.4.42, 3.5.28, and 3.6.9 contain a patch. If upgrading is not immediately possible, reduce exposure by treating the affected RPCs as unauthenticated in practice. Restrict network access to etcd server ports so only trusted components can connect and/or require strong client identity at the transport layer, such as mTLS with tightly scoped client certificate distribution.
— NVD
etcd: Authorization bypasses in multiple APIs
— Microsoft
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
go/go.etcd.io/etcd/v3to a version that resolves this vulnerability.Fixed in 3.4.42 - Upgrade
Upgrade
go/go.etcd.io/etcd/v3to a version that resolves this vulnerability.Fixed in 3.5.28 - Upgrade
Upgrade
go/go.etcd.io/etcd/v3to a version that resolves this vulnerability.Fixed in 3.6.9 - Configuration
Require strong client identity at the transport layer by configuring mutual TLS (mTLS) for etcd client connections and issue tightly scoped client certificates only to trusted clients.
etcd transport-layer client identity (mTLS) = require mTLS with tightly scoped client certificates - Compensating control
Restrict network access to etcd server ports so only trusted components can connect (for example, apply firewall rules or network ACLs to limit access to etcd gRPC/API ports to known/trusted IPs or subnets).