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etcd: Nested etcd transactions bypass RBAC authorization checks

Low severity GitHub Reviewed Published Mar 20, 2026 in etcd-io/etcd • Updated Mar 27, 2026

Package

gomod go.etcd.io/etcd (Go)

Affected versions

<= 3.3.27

Patched versions

None
gomod go.etcd.io/etcd/v3 (Go)
>= 3.6.0-alpha.0, <= 3.6.8
>= 3.5.0-alpha.0, <= 3.5.27
<= 3.4.41
3.6.9
3.5.28
3.4.42

Description

Impact

What kind of vulnerability is it? Who is impacted?

An authenticated user with RBAC restricted permissions on key ranges can use nested transactions to bypass all key-level authorization. This allows any authenticated user with direct access to etcd to effectively ignore all key range restrictions, accessing the entire etcd data store.

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?

This vulnerability is 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

Our community helps keep etcd secure

SIG-Etcd thanks community members Luke Francis and Battulga Byambaa for reporting this vulnerability.

References

@ahrtr ahrtr published to etcd-io/etcd Mar 20, 2026
Published to the GitHub Advisory Database Mar 20, 2026
Reviewed Mar 20, 2026
Published by the National Vulnerability Database Mar 26, 2026
Last updated Mar 27, 2026

Severity

Low

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:N

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(8th percentile)

Weaknesses

Incorrect Authorization

The product performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check. Learn more on MITRE.

CVE ID

CVE-2026-33343

GHSA ID

GHSA-rfx7-8w68-q57q

Source code

Credits

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