MCP PHP SDK: client HttpTransport SSE buffer (sseBuffer .= chunk) grows unbounded when server withholds the event del...

Date Aug 19, 2026

Type Vendor advisory

Signal High-risk advisory

Vendor / Product Composer · mcp/sdk

CVE CVE-2026-53965

High-risk advisory CVE-2026-53965

Summary

MCP PHP SDK: client HttpTransport SSE buffer (sseBuffer .= chunk) grows unbounded when server withholds the event delimiter

Why it matters

GitHub has published a reviewed security advisory for mcp/sdk. Prioritize it with other application dependency updates.

Operator check

Check whether mcp/sdk is present in application dependency manifests, lockfiles, or build images. Review the GitHub advisory and upgrade to a patched version where available. CVSS score: 8.7.

Sources

GitHub Advisory GHSA-7m52-jw36-44r3 NVD — CVE-2026-53965 Source reference

PatchBrief uses public sources. It does not scan environments, verify exposure, or replace vendor guidance.

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