vulnerability / NVI-00015297 / Revision 1
MCP Ruby SDK: Unbounded line buffer in stdio transports leads to memory exhaustion (DoS)
GitHub lists this reviewed advisory for mcp. Published version ranges and source prerequisites are shown below; this is not an inspection of a visitor’s application.
This report has not inspected your inventory, configuration, deployed build, reachability or evidence. A catalog listing and a severity score do not establish exposure or compromise.
01 / Meaning
Why it matters
Published affected context helps an owner decide what evidence to gather. This report has not examined your application.
6.2 medium
GitHub source severity; exploitability and local consequence require separate evidence.
As of · GitHub Advisory Database
02 / Applicability
The affected context
Affected versions, configuration prerequisites and known exclusions are public. Confirm each one against the deployed service.
mcp
source listed<= 0.22.0
## Summary The stdio transports in `MCP::Server::Transports::StdioTransport` and `MCP::Client::Stdio` read newline-delimited JSON-RPC frames using `IO#gets` with no `limit` argument. CRuby's `IO#gets` with no limit reads from the current position until the next separator (`\n`) with no upper bound on the returned string length. A peer that streams bytes without ever emitting a newline causes `gets` to accumulate the entire stream in a single Ruby `String` until the process is killed by the operating-system OOM killer. This is the same vulnerability class tracked in sibling MCP SDKs as GHSA-74gp-qhv5-v493 (Kotlin), GHSA-wqgc-pwpr-pq7r (TypeScript), GHSA-655q-2283-6jgj (Python), and others. It was identified during a cross-SDK audit; ruby-sdk had no prior report. ## Affected code Verified at `main` @ `cf44475c`. ### Server transport — `lib/mcp/server/transports/stdio_transport.rb` ```ruby # line 23 while @open && (line = $stdin.gets) # <-- no limit argument response = @session.handle_json(line.strip) ... # line 76 while @open && (line = $stdin.gets)
03 / Response
What to do next
- investigate
Identify the exact component and deployed version, examine the linked publisher’s conditions, and retain evidence of any mitigation.
Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system. GitHub Advisory Database
A fixed release is not deployment evidence.
Check current vendor support and compatibility. After making a change, verify the deployed build and relevant runtime conditions. Keep the evidence, owner and time. An updated lockfile alone does not prove what is running.
04 / Limits
What this report cannot establish
- Customer inventory, deployment, reachability and exploitation have not been inspected.
05 / Provenance
Sources you can inspect
Each assertion retains its source. Mirrored records may repeat one underlying publisher; additional links are not independent corroboration.
- GHSA-7683-3w9x-ch42 ↗
GitHub Advisory Database · vendor advisory
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Public revision history
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- Revision 1 ·
First indexed by Null; source disclosure date is shown separately.