Auth bypass in Lfprojects Mcp_ruby_sdk
CVE-2026-33946
MCP Ruby SDK is the official Ruby SDK for Model Context Protocol servers and clients. Prior to version 0.9.2, the Ruby SDK's streamable_http_transport.rb implementation contains a session hijacking vulnerability. An attacker who obtains a…
EPSS: 0.005 (37.8th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 5.9 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N.
Affected products
- Lfprojects Mcp_ruby_sdk
- Modelcontextprotocol Ruby-sdk — versions < 0.9.2
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM, Exploit, Vendor Advisory)
- security-advisories@github.com (Patch, x_refsource_MISC)
- security-advisories@github.com (Permissions Required, x_refsource_MISC)
- security-advisories@github.com (Patch, x_refsource_MISC)
- security-advisories@github.com (Patch, x_refsource_MISC)
- security-advisories@github.com (Patch, x_refsource_MISC)
- security-advisories@github.com (Patch, x_refsource_MISC)
- security-advisories@github.com (Product, x_refsource_MISC, Release Notes)
Frequently asked questions
- What is CVE-2026-33946?
- CVE-2026-33946 is a medium-severity vulnerability in Lfprojects Mcp_ruby_sdk, classified under Session Fixation. CVSS score: 5.9/10. Published 2026-03-27.
- How severe is CVE-2026-33946?
- Medium severity. CVSS v3 base score is 5.9 out of 10.