Missing Authorization in MCP Python SDK - CVE-2026-52870

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Main Vulnerability Database Vulnerabilities #VU163089

Missing Authorization in MCP Python SDK - CVE-2026-52870

Published: November 9, 2026


Vulnerability identifier: #VU163089
CSH Severity: Low
CVSS v4: 7.2 [CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:L/VA:L/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-52870
CWE-ID: CWE-862
Exploitation vector: Remote access
Exploit availability: No public exploit available

Vulnerability details

The vulnerability allows a low-privileged remote attacker to read other clients' task results and cancel their tasks.

The vulnerability exists due to missing session ownership checks in the MCP Python SDK's default task handlers when a multi-client server calls server.experimental.enable_tasks(). A low-privileged remote attacker can enumerate tasks and retrieve queued elicitation payloads, preventing intended recipients from receiving those messages.


Affected software

MCP Python SDK
watsonx.data

How to mitigate CVE-2026-52870

Install security update from vendor's website.

MCP Python SDK - update to 1.27.2

External References

Related Security Bulletins