CVE-2026-53937Public exploit

Host-process crash via unbounded stdio frame buffering

Published Sep 8, 2026 · Updated Sep 8, 2026

Resource exhaustion in MCP Kotlin SDK 0.7.0 through 0.12.0 allows remote attackers to crash a host process via unframed stdio input. ReadBuffer.append retains every byte until a newline appears, while unlimited transport channels add queued chunks without a size cap or backpressure. Exploitation requires attacker-controlled input to reach a stdio transport, where memory growth ends in OutOfMemoryError or host OOM termination.

CVSS severity6.2
Medium
EPSS probability0.19%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Resource exhaustion in MCP Kotlin SDK 0.7.0 through 0.12.0 allows remote attackers to crash a host process via unframed stdio input. ReadBuffer.append retains every byte until a newline appears, while unlimited transport channels add queued chunks without a size cap or backpressure. Exploitation requires attacker-controlled input to reach a stdio transport, where memory growth ends in OutOfMemoryError or host OOM termination.

The record

CVE
CVE-2026-53937
Published
Sep 8, 2026
Updated
Sep 8, 2026
Vendor
Model Context Protocol
Product
MCP Kotlin SDK Core
Classifications
CWE-400, CWE-770, T1499.003
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 8, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 8, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 0.13.0

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Model Context Protocol · MCP Kotlin SDK Coreversion=< 0.13.0
Model Context Protocol · MCP Kotlin SDK Serverversion=>= 0.7.0, < 0.13.0
Model Context Protocol · MCP Kotlin SDKversion=< 0.13.0
Model Context Protocol · MCP Kotlin SDK Clientversion=>= 0.7.0, < 0.13.0

Published CVSS scores

6.2GitHubCVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-400Uncontrolled Resource Consumption
CWE-770Allocation of Resources Without Limits or Throttling
T1499.003Application Exhaustion Flood

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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