CVE-2026-53602
Received Received - Intake

Authorization Bypass in Nebula-Mesh VPN

Publication date: 2026-09-04

Last updated on: 2026-09-04

Assigner: GitHub, Inc.

Description
nebula-mesh is a self-hosted control plane for Slack Nebula mesh VPN. Prior to version 0.3.7, two related authorization gaps let a host that should no longer be trusted obtain a fresh, valid Nebula certificate, because nebula-mgmt does not re-evaluate revocation/authorization state at certificate issuance time — only at poll time. Firstly, the blocklist is not enforced at sign / re-enroll time. internal/api/enroll.go:128 calls caMgr.Sign(...) without consulting the blocklist. The blocklist is only checked in the poll path (internal/api/updates.go:57, fingerprintInBlocklist). The blocklist is keyed by certificate fingerprint (internal/store/sqlite.go), so a re-enrollment produces a new fingerprint that is not in the blocklist. Secondly, renewal does not re-validate operator / CA status. Auto-renewal at poll time (internal/api/updates.go:285-319, signHostCert) reads host.Name, host.Groups, host.NebulaIPs from the DB and re-signs without checking whether the owning operator is still active or the CA still valid. DisableOperator (internal/store/sqlite_operators.go) revokes sessions and API keys but does not retire the operator's CAs, and pki/signer.go checks only CA cert time-expiry, not operator/CA status. This issue has been patched in version 0.3.7.

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Meta Information

Published
2026-09-04
Last Modified
2026-09-04
Generated
2026-09-05
AI Q&A
2026-09-04
EPSS Evaluated
N/A
NVD
CVE-2026-53602

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
nebula-mesh nebula to 0.3.7 (exc)

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-285 The product does not perform or incorrectly performs an authorization check when an actor attempts to access a resource or perform an action.
CWE-862 The product does not perform an authorization check when an actor attempts to access a resource or perform an action.

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Executive Summary

This vulnerability in nebula-mesh (before version 0.3.7) allows a previously trusted host to obtain a new valid certificate even after being revoked. The issue occurs because the system does not check revocation status during certificate issuance or renewal, only during periodic updates. A revoked host can re-enroll with a new fingerprint, bypassing the blocklist, and auto-renewal does not verify if the operator or CA remains valid.

Detection Guidance

This vulnerability cannot be directly detected through standard network or system commands because it involves a logic flaw in the nebula-mesh certificate issuance process. The issue requires checking if the blocklist is enforced during certificate renewal and if operator/CA status is validated. Manual code review of internal/api/enroll.go and internal/api/updates.go is necessary to confirm the presence of the vulnerability.

Impact Analysis

An attacker or previously trusted host could regain access to the VPN by obtaining a new certificate, even after being revoked. This could lead to unauthorized network access, data breaches, or continued use of compromised systems. The impact includes potential loss of network integrity and confidentiality.

Compliance Impact

This vulnerability could violate compliance requirements that mandate strict access controls and timely revocation of unauthorized access (e.g., GDPR's data protection principles or HIPAA's access controls). Failure to revoke access properly may result in non-compliance, leading to legal penalties or data exposure risks.

Mitigation Strategies

Upgrade nebula-mesh to version 0.3.7 or later to address the authorization gaps in certificate issuance and renewal processes.

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