dbcve.org
Mcp Python SdkApplication · Lfprojects

CVE-2026-52870

HIGH · 7.6 CVSS v3.1 Published 2026-07-15
Fix available
A fix is available. Upgrade to 1.27.2 or later.
See remediation →
82/100
Remediation priority · High
Remotely reachable Zero-click 5 weeks old

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
The MCP Python SDK, called mcp on PyPI, is a Python implementation of the Model Context Protocol (MCP). From 1.23.0 until 1.27.2, default handlers installed by server.experimental.enable_tasks() for tasks/list, tasks/get, tasks/result, and tasks/cancel operate only on task identifiers without recording the session that created each task, allowing any connected client to enumerate, read results from, consume messages for, or cancel other clients' tasks. This issue is fixed in version 1.27.2.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

The MCP Python SDK's experimental task handlers (tasks/list, tasks/get, tasks/result, tasks/cancel) do not associate tasks with the session that created them, allowing any connected client to enumerate, read, consume, or cancel other clients' tasks due to missing session-based authorization checks.

MitigationUpgrade the mcp package to version 1.27.2 or later, which implements session tracking for tasks.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Mcp Python SdkApplication
Affected:>= 1.23.0, < 1.27.2

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
Low
Availability
Low

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:L

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Check installed MCP Python SDK version
    Run 'pip show mcp' or 'pip list | grep mcp' to display the installed version of the mcp package
    Affected if The installed version is >= 1.23.0 and < 1.27.2
  2. Verify experimental task handlers are exposed
    Inspect your MCP server configuration or code to determine if the experimental task handlers (tasks/list, tasks/get, tasks/result, tasks/cancel) are registered and accessible to clients
    Affected if Any of these task handlers are enabled and accessible to clients on the server
  3. Confirm multiple client sessions can connect
    Review server configuration or logs to determine if more than one client can simultaneously connect to the MCP server
    Affected if The server allows multiple concurrent client connections, enabling cross-session task access
  4. Test cross-client task access
    If multiple clients can connect, verify whether a client can enumerate, read, consume, or cancel tasks created by a different client session by calling the task handlers from an unauthorized session
    Affected if Clients can access or manipulate tasks created by other sessions without authorization

The environment is affected if the MCP Python SDK version is between 1.23.0 and 1.27.2 (exclusive), experimental task handlers are enabled, and multiple clients can connect, allowing unauthorized cross-session task access.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 1.27.2 or later
Fixed in 1.27.2
Interim mitigation

Upgrade the mcp package to version 1.27.2 or later, which implements session tracking for tasks.

Recommended fix High confidence

1.27.2

  1. 1. Identify the current version of mcp (MCP Python SDK) installed in your environment using `pip show mcp` or `pip list | grep mcp`
  2. 2. If the installed version is >= 1.23.0 and < 1.27.2, upgrade to version 1.27.2 or later using: `pip install --upgrade mcp>=1.27.2`
  3. 3. Verify the upgrade was successful by checking the installed version again with `pip show mcp`
  4. 4. If your application uses `server.experimental.enable_tasks()`, ensure it is updated to the new version and test that task operations are now properly scoped to the session that created each task

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Mcp Python Sdk Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
11.0 hours of engineering $1,930
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,088.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2026-52870 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-52870 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data