Connect your agent
AdvisoriesCriticalCheck your lockfilePluginHow it worksPricing Connect your agent

Advisory record · GHSA-7m52-jw36-44r3

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

CVSS 6.9 MediumEPSS 0.0062 · 50th percentile

Published by the GitHub Advisory Database at 19 Aug 2026, 19:17 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

PackageEcosystemAffectedFixed in
mcp/sdkPackagist>=0.5.0, <0.7.10.7.1
Identifiers
GHSA-7m52-jw36-44r3 · CVE-2026-53965 · PKSA-p9gd-j6gr-6f9t
Weakness (CWE)
CWE-400 · CWE-770
Tags
Published
19 Aug 2026
Updated
19 Aug 2026

Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

The HTTP client transport in mcp/sdk 0.5.0 before 0.7.1 buffers incoming Server-Sent Events data without a size limit. A malicious server, or an attacker who can alter responses on a plaintext connection, can stream data without an event delimiter to exhaust client memory and crash the client. Upgrade to mcp/sdk 0.7.1.

Written 3 Nov 2026.

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

ScoreRatingCVSSVectorSource
6.9 Medium 4.0 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N CNA (GitHub_M)
  • CISA KEV Not listed.
  • EPSS 0.0062, the 50th percentile, on 14 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

  1. 31 Oct 2026, 14:24 UTC First seen by agentprime
  2. 31 Oct 2026, 14:24 UTC Confirmed by OSV

Sources

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.