CVE-2026-63119: modelcontextprotocol ruby-sdk Uncontrolled Resource Consumption
Vulnerability summary
CVE-2026-63119 is a medium (CVSS 6.2) Uncontrolled Resource Consumption vulnerability in modelcontextprotocol ruby-sdk. EPSS estimates a 0.18% chance of exploitation in the next 30 days, higher than 7.4% of scored vulnerabilities.
Timeline
- 29-07-2026PublishedVulnerability first disclosed.
- 29-07-2026Last modifiedVulnerability information updated.
Description
MCP Ruby SDK is the official Ruby SDK for Model Context Protocol servers and clients. Prior to 0.23.0, MCP::Server::Transports::StdioTransport and MCP::Client::Stdio in the mcp gem use IO#gets without a byte limit, allowing a peer that sends data without a newline to exhaust process memory. This issue is fixed in version 0.23.0.
CVSS metrics
3 scores · 3 sources · 1 version- OSV · RubygemsEcosystem advisory · calculated6.2MediumCVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- NVDNIST6.2MediumCVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS trend
Probability
0.18%
Chance of exploitation in the next 30 days
Percentile
7%
Versus all other CVEs
30-day change
+0.06 pp
From 0.13% on 19-09-2026
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root cause- CWE-400Uncontrolled Resource ConsumptionThe product does not properly control the allocation and maintenance of a limited resource.
- CWE-770Allocation of Resources Without Limits or ThrottlingThe product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated.
Affected systems
Modelcontextprotocol1 product
- ruby-sdk< 0.23.0
RubyGems1 product
- mcp< 0.23.0
2 vendors · 2 products
References
5 links- github.com/modelcontextprotocol/ruby-sdk/security/advisories/GHSA-7683-3w9x-ch42X Refsource CONFIRMWEB
