Missing Release of Resource after Effective Lifetime Affecting mcp package, versions [1.8.0,1.30.0)[2.0.0,2.2.0)
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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- published18 Oct 2026
- disclosed15 Oct 2026
- creditNikhil Kumar, evilgensec, Madan301
Introduced: 15 Oct 2026
NewCVE-2026-59951 (opens in a new tab)How to fix?
Upgrade mcp to version 1.30.0, 2.2.0 or higher.
Overview
mcp is a Model Context Protocol SDK
Affected versions of this package are vulnerable to Missing Release of Resource after Effective Lifetime via StreamableHTTPSessionManager in streamable_http_manager.py, which prior to this fix neither expired idle stateful sessions nor capped the number of concurrent sessions. An unauthenticated remote attacker can open an unbounded number of Streamable HTTP sessions and hold them open indefinitely, exhausting server memory and causing a crash.