CVE-2026-53965: MCP PHP SDK unbounded memory buffer vulnerability
MCP PHP SDK
The Model Context Protocol PHP SDK has an unbounded memory buffer vulnerability in its HTTP client transport during SSE stream processing. A malicious server can cause unlimited memory growth leading to a denial of service.
disclosed CVENo confirmed exploitation, so this record is tracked as a disclosed vulnerability and not counted as an incident. It moves into the counts if CISA or the vendor confirms exploitation. Why
- CVSS
- 8.7
- EPSS
- 0.01 · top 50% · 2026-11-13
- fix status
- Fix status unknown
- first report
- 25 Aug 2026
- last update
- 25 Aug 2026
- CVE ids
Timeline · 1
Sources · 1
Advisories and databases
- 2026-08-25CVE-2026-53965: The MCP PHP SDK (Composer package mcp/sdk) is the official Model Context Protocol SDK for PHP.NVD · nvd.nist.gov/vuln/detail/CVE-2026-53965
Titles and links belong to their publishers. The summary above is written by gcdRadar in its own words; data is CC BY-SA 4.0.
Classification
- lane
- Patch now
- AI role
- Attack on AI
- categories
- Infrastructure vulnerability
- severity
- 2 · Disclosed vulnerability
- fix status
- Fix status unknown
- targets
- Framework / tooling
- owasp llm top 10
- LLM03:2025 Supply Chain
- mitre atlas
- no technique for these categories
- tags
- mcp
- dates
- happened 25 Aug 2026 · first reported 25 Aug 2026
- origin
- NVDVulnerability record from NVD / the GitHub Advisory Database. This product uses the NVD API but is not endorsed or certified by the NVD.
- record
- confidence 0.95 · created 2026-10-18 10:04Z · updated 2026-10-18 10:04Z
Lane, AI role, categories and severity come from the classifier; the OWASP and ATLAS rows are derived from the categories. How these are assigned
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the brief as text
# CVE-2026-53965: MCP PHP SDK unbounded memory buffer vulnerability https://gcdradar.vercel.app/incidents/cve-2026-53965-mcp-php-sdk-unbounded-memory-buffer-vulnerabi · AIR-2026-1293 · closed 2026-08-25 - Lane: Patch now - Severity: 2 (Disclosed vulnerability) - Fix status: Fix status unknown - First reported: 2026-08-25 - AI role: Attack on AI - Products: MCP PHP SDK - CVE ids: CVE-2026-53965 - CVSS: 8.7 ## Summary The Model Context Protocol PHP SDK has an unbounded memory buffer vulnerability in its HTTP client transport during SSE stream processing. A malicious server can cause unlimited memory growth leading to a denial of service. ## What to do No action recorded; read the sources below and the vendor's advisory. ## Latest updates - 2026-08-25: CVE-2026-53965: The MCP PHP SDK (Composer package mcp/sdk) is the official Model Context Protocol SDK for PHP. (https://nvd.nist.gov/vuln/detail/CVE-2026-53965) ## Sources - 2026-08-25 NVD: CVE-2026-53965: The MCP PHP SDK (Composer package mcp/sdk) is the official Model Context Protocol SDK for PHP. https://nvd.nist.gov/vuln/detail/CVE-2026-53965 Verify against the vendor's advisory before changing production. Data CC BY-SA 4.0, https://gcdradar.vercel.app.
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