MCP Kotlin SDK's unbounded line buffer in StdioServerTransport/StdioClientTransport leads to memory exhaustion (DoS)
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | ||||||
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| modelcontextprotocol | io.modelcontextprotocol:kotlin-sdk | affected |
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| modelcontextprotocol | io.modelcontextprotocol:kotlin-sdk-client | affected |
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| modelcontextprotocol | io.modelcontextprotocol:kotlin-sdk-core | affected |
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| modelcontextprotocol | io.modelcontextprotocol:kotlin-sdk-server | affected |
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No data.
No data.
| Vendor | Product | Versions | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Modelcontextprotocol | Io.modelcontextprotocol:kotlin-sdk |
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| Modelcontextprotocol | Io.modelcontextprotocol:kotlin-sdk-client |
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| Modelcontextprotocol | Io.modelcontextprotocol:kotlin-sdk-core |
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| Modelcontextprotocol | Io.modelcontextprotocol:kotlin-sdk-server |
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No CVSS v4.0
No CVSS v3.0
No CVSS v2
This CVE is not in the KEV list.
Exploit prediction score: < 1% (0.186% probability within 30 days)
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ssvc
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| First Time appeared |
Modelcontextprotocol
Modelcontextprotocol io.modelcontextprotocol:kotlin-sdk Modelcontextprotocol io.modelcontextprotocol:kotlin-sdk-client Modelcontextprotocol io.modelcontextprotocol:kotlin-sdk-core Modelcontextprotocol io.modelcontextprotocol:kotlin-sdk-server |
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| Vendors & Products |
Modelcontextprotocol
Modelcontextprotocol io.modelcontextprotocol:kotlin-sdk Modelcontextprotocol io.modelcontextprotocol:kotlin-sdk-client Modelcontextprotocol io.modelcontextprotocol:kotlin-sdk-core Modelcontextprotocol io.modelcontextprotocol:kotlin-sdk-server |
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| Description | MCP Kotlin SDK is the Kotlin Multiplatform software development kit for the Model Context Protocol. In versions 0.7.0 through 0.12.0, `ReadBuffer.append` in `kotlin-sdk-core/src/commonMain/kotlin/io/modelcontextprotocol/kotlin/sdk/shared/ReadBuffer.kt` writes every chunk of bytes received from the stdio transport into a `kotlinx.io.Buffer` with no size cap. Frames are extracted from that buffer only when a `\n` (0x0a) byte is observed. A peer that streams bytes without ever sending a newline causes the internal buffer to grow indefinitely until the JVM (or the surrounding host process) is OOM-killed. The leak is amplified by `StdioServerTransport` and `StdioClientTransport`, which both queue raw chunks through a `kotlinx.coroutines.channels.Channel<ByteArray>(Channel.UNLIMITED)` and then call `readBuffer.append(chunk)` without backpressure or size guard. This is a remote-pre-auth denial of service whenever an SDK stdio server's stdin is fed by an untrusted or attacker-controlled producer (for example: a host program that exec's the MCP server as a subprocess and pipes through bytes received from a network peer, or a sidecar wrapper that proxies bytes from an HTTP endpoint to the stdio transport). Version 0.13.0 fixes the issue. | |
| Title | MCP Kotlin SDK's unbounded line buffer in StdioServerTransport/StdioClientTransport leads to memory exhaustion (DoS) | |
| Weaknesses | CWE-400 CWE-770 |
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| Metrics |
cvssV3_1
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