CVE-2026-63119

MEDIUMPre-NVD 6.26.2—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 6.2 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.1%, top 97% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
Elevated
6.2EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 6.2Exploit: Elevated riskExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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 v3
6.2
EG Score
6.2(medium)
EG Risk
44(Track)
EG Risk 44/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity62% × 45%
Exploitation40% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
3%
KEV
Not listed

Published

July 29, 2026

Last Modified

July 30, 2026

Advisory Details (3)

Auto-updated Jul 29, 2026
🔬 Proof of concept available. Patch available. Sources: github, github_commit, github_release.
github_release Patch Available

v0.23.0

Patch available: modelcontextprotocol/ruby-sdk v0.23.0

https://github.com/modelcontextprotocol/ruby-sdk/releases/tag/v0.23.0
github_commit Patch Available

commit 267b8fa62854 (modelcontextprotocol/ruby-sdk)

Patch available: modelcontextprotocol/ruby-sdk v0.23.0 (contains commit 267b8fa62854)

https://github.com/modelcontextprotocol/ruby-sdk/commit/267b8fa6285453525c81ce43db6b7dcd7a8a8c2f
github Patch Available🟡 PoC Available

Unbounded line buffer in stdio transports leads to memory exhaustion (DoS) · Advisory · modelcontextprotocol/ruby-sdk · GitHub

https://github.com/modelcontextprotocol/ruby-sdk/security/advisories/GHSA-7683-3w9x-ch42

Vendor Advisories for CVE-2026-63119(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Affected Packages

(1 across 1 ecosystem)
RubyGems(1)
PackageVulnerable rangeFixed inDependents
mcp0.1.0 ... 0.9.2 (25 versions)0.23.0—

Weakness Classification(2)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 8× in last 7d / 43× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-09-15 07:47 UTCEG score recompute
  2. 2026-09-14 06:45 UTCEG score recompute
  3. 2026-09-13 06:58 UTCEG score recompute
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  5. 2026-09-11 14:53 UTCEPSS rescore
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  1. 2026-08-28 21:42 UTCEPSS rescore
  2. 2026-08-27 20:55 UTCEG score recompute
  3. 2026-08-27 14:25 UTCEPSS rescore
  4. 2026-08-26 19:37 UTCEG score recompute
  5. 2026-08-26 14:46 UTCEPSS rescore
  6. 2026-08-25 18:20 UTCEG score recompute
  7. 2026-08-25 13:49 UTCEPSS rescore
  8. 2026-08-24 18:33 UTCEG score recompute
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  10. 2026-08-23 00:19 UTCEPSS rescore
  11. 2026-08-22 18:59 UTCEG score recompute
  12. 2026-08-21 23:49 UTCEPSS rescore
  13. 2026-08-19 19:38 UTCEG score recompute
  14. 2026-08-19 17:04 UTCEPSS rescore
  15. 2026-08-18 18:33 UTCEG score recompute
  16. 2026-08-18 13:48 UTCEPSS rescore
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  19. 2026-08-16 16:09 UTCEG score recompute
  20. 2026-08-16 14:56 UTCEPSS rescore
  21. 2026-08-15 16:23 UTCEG score recompute
  22. 2026-08-15 01:30 UTCEPSS rescore
  23. 2026-08-14 16:36 UTCEG score recompute
  24. 2026-08-13 22:00 UTCEPSS rescore
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  26. 2026-08-12 13:51 UTCEPSS rescore
  27. 2026-08-11 17:05 UTCEG score recompute
  28. 2026-08-11 00:00 UTCEPSS rescore
  29. 2026-08-09 17:31 UTCEG score recompute
  30. 2026-08-09 13:47 UTCEPSS rescore
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  32. 2026-08-08 16:37 UTCEPSS rescore
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  34. 2026-08-06 13:47 UTCEPSS rescore
  35. 2026-08-05 19:17 UTCEPSS rescore
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  37. 2026-08-04 18:38 UTCEG score recompute
  38. 2026-08-04 15:10 UTCEPSS rescore
  39. 2026-08-04 10:39 UTCEPSS rescore
  40. 2026-08-03 18:51 UTCEG score recompute
  41. 2026-08-03 10:36 UTCEPSS rescore
  42. 2026-08-02 19:05 UTCEG score recompute
  43. 2026-08-02 02:27 UTCEPSS rescore
  44. 2026-08-01 19:18 UTCEG score recompute
  45. 2026-08-01 04:16 UTCEPSS rescore
  46. 2026-07-30 19:43 UTCEG score recompute
  47. 2026-07-30 16:28 UTCEPSS rescore
  48. 2026-07-29 20:20 UTCEG score recompute
  49. 2026-07-29 19:59 UTCEG score recompute
  50. 2026-07-29 19:23 UTCEG score recompute
  51. 2026-07-29 19:22 UTCMITRE cvelistV5first tracked

Frequently asked(5)

What is CVE-2026-63119?
CVE-2026-63119 is a medium vulnerability published on July 29, 2026. 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…
When was CVE-2026-63119 disclosed?
CVE-2026-63119 was first published in the National Vulnerability Database on July 29, 2026, with the most recent update on July 30, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-63119 actively exploited?
CVE-2026-63119 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 97.3% of all scored CVEs.
What is the CVSS score of CVE-2026-63119?
CVE-2026-63119 has a CVSS v3 base score of 6.2 (NVD).
How do I remediate CVE-2026-63119?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-63119, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-63119

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