Authentication Bypass in Relay Server by No Instructions
CVE-2026-42889

9.1CRITICAL

Key Information:

Vendor

No-instructions

Status
Relay-server
Vendor
CVE Published:
12 May 2026

What is CVE-2026-42889?

Relay Server versions 0.9.0 through 0.9.6 are susceptible to an authentication bypass in their multi-document WebSocket endpoints. When configured for authentication, the server incorrectly grants full permissions to WebSocket connections that lack a token query parameter, allowing potential unauthorized users to access and modify document contents if they know a document ID. This serious oversight exposes sensitive data and can compromise document integrity, underscoring the importance of updating to version 0.9.7, which addresses this vulnerability.

Affected Version(s)

relay-server >= 0.9.0, < 0.9.7

References

https://github.com/No-Instructions/relay-server/security/...
x_refsource_CONFIRM

CVSS V3.1

Score:
9.1
Severity:
CRITICAL
Confidentiality:
High
Integrity:
High
Availability:
High
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

.