CVE-2026-34742

HIGHNVD 8.18.1—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 8.1 under NVD CVSS v3. EPSS exploit probability: 0.0%, top 91% 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, nvd
8.1
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 0%CVSS: 8.1Exploit: NoneExposed: 0

A fix is available — apply it.

The Go MCP SDK used Go's standard encoding/json. Prior to version 1.4.0, the Model Context Protocol (MCP) Go SDK does not enable DNS rebinding protection by default for HTTP-based servers. When an HTTP-based MCP server is run on localhost without authentication with StreamableHTTPHandler or SSEHandler, a malicious website could exploit DNS rebinding to bypass same-origin policy restrictions and send requests to the local MCP server. This could allow an attacker to invoke tools or access resources exposed by the MCP server on behalf of the user in those limited circumstances. This issue has been patched in version 1.4.0.

CVSS v3
8.1
EG Score
8.1(medium)
EG Risk
—
EPSS
37.0%
KEV
Not listed

Published

April 2, 2026

Last Modified

July 15, 2026

Advisory Details (4)

Auto-updated Jun 10, 2026
Patch available. Sources: github, github_commit, github_pr, github_release.
github Patch Available

DNS Rebinding Protection Disabled by Default in Model Context Protocol Go SDK for Servers Running on Localhost · Advisory · modelcontextprotocol/go-sdk · GitHub

https://github.com/modelcontextprotocol/go-sdk/security/advisories/GHSA-xw59-hvm2-8pj6
github_release Patch Available

v1.4.0

Patch available: modelcontextprotocol/go-sdk v1.4.0

https://github.com/modelcontextprotocol/go-sdk/releases/tag/v1.4.0
github_pr Patch Available

feat: add automatic DNS rebinding protection for localhost servers

Patch available: modelcontextprotocol/go-sdk v1.4.0 (PR #760 merged 2026-02-13)

https://github.com/modelcontextprotocol/go-sdk/pull/760
github_commit Patch Available

commit 67bd3f2e2b53 (modelcontextprotocol/go-sdk)

Patch available: modelcontextprotocol/go-sdk v1.4.0 (contains commit 67bd3f2e2b53)

https://github.com/modelcontextprotocol/go-sdk/commit/67bd3f2e2b53ce11a16db8d976cdb8ff1e986b6d

Vendor Advisories for CVE-2026-34742(2)

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

Patch Availability(1)

Vendor / EcosystemFixed in / PatchReleasedSource
redhatdevspaces/udi-rhel9:17798297362026-05-28redhat

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Affected Packages

(1 across 1 ecosystem)
Go(1)
PackageVulnerable rangeFixed inDependents
github.com/modelcontextprotocol/go-sdk—1.4.0—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 8× in last 7d / 41× 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.

Showing the most recent 100 of 105 total refreshes for this CVE.

  1. 2026-07-22 14:08 UTCEPSS rescore
  2. 2026-07-21 15:24 UTCEPSS rescore
  3. 2026-07-20 17:08 UTCEPSS rescore
  4. 2026-07-19 14:31 UTCEPSS rescore
  5. 2026-07-19 02:29 UTCEPSS rescore
  6. 2026-07-18 10:04 UTCEPSS rescore
  7. 2026-07-17 03:24 UTCOSV refresh
  8. 2026-07-16 17:03 UTCEPSS rescore
  9. 2026-07-15 16:57 UTCEPSS rescore
  10. 2026-07-15 16:57 UTCEPSS rescore
  11. 2026-07-15 02:23 UTCNVD updateCVSS v3 → 8.1
  12. 2026-07-15 02:00 UTCEPSS rescore
  13. 2026-07-15 01:21 UTCMITRE cvelistV5CVSS v3 → 8
  14. 2026-07-13 22:30 UTCEPSS rescore
  15. 2026-07-13 06:13 UTCEPSS rescore
  16. 2026-07-13 06:13 UTCEPSS rescore
  17. 2026-07-12 05:46 UTCEPSS rescore
  18. 2026-07-11 08:27 UTCEPSS rescore
  19. 2026-07-09 19:10 UTCEPSS rescore
  20. 2026-07-08 15:15 UTCEPSS rescore
  21. 2026-07-07 13:46 UTCEPSS rescore
  22. 2026-07-06 16:27 UTCEPSS rescore
  23. 2026-07-06 16:27 UTCEPSS rescore
  24. 2026-07-06 02:23 UTCEPSS rescore
  25. 2026-07-06 02:23 UTCEPSS rescore
Show 75 more
  1. 2026-07-05 02:30 UTCEPSS rescore
  2. 2026-07-04 06:31 UTCEPSS rescore
  3. 2026-07-01 15:06 UTCEPSS rescore
  4. 2026-06-30 23:22 UTCEPSS rescore
  5. 2026-06-29 14:06 UTCEPSS rescore
  6. 2026-06-29 14:06 UTCEPSS rescore
  7. 2026-06-28 14:07 UTCEPSS rescore
  8. 2026-06-28 14:07 UTCEPSS rescore
  9. 2026-06-28 04:56 UTCEPSS rescore
  10. 2026-06-28 04:56 UTCEPSS rescore
  11. 2026-06-27 03:08 UTCEPSS rescore
  12. 2026-06-25 13:49 UTCEPSS rescore
  13. 2026-06-25 13:49 UTCEPSS rescore
  14. 2026-06-24 14:05 UTCEPSS rescore
  15. 2026-06-23 21:33 UTCEPSS rescore
  16. 2026-06-23 21:33 UTCEPSS rescore
  17. 2026-06-22 14:25 UTCEPSS rescore
  18. 2026-06-22 14:25 UTCEPSS rescore
  19. 2026-06-21 14:56 UTCEPSS rescore
  20. 2026-06-21 14:56 UTCEPSS rescore
  21. 2026-06-21 01:59 UTCEPSS rescore
  22. 2026-06-19 19:25 UTCEPSS rescore
  23. 2026-06-19 19:25 UTCEPSS rescore
  24. 2026-06-18 17:52 UTCEPSS rescore
  25. 2026-06-18 17:52 UTCEPSS rescore
  26. 2026-06-17 17:53 UTCEPSS rescore
  27. 2026-06-16 17:52 UTCEPSS rescore
  28. 2026-06-15 17:49 UTCEPSS rescore
  29. 2026-06-14 23:18 UTCEPSS rescore
  30. 2026-06-13 23:00 UTCEPSS rescore
  31. 2026-06-12 23:12 UTCEPSS rescore
  32. 2026-06-12 23:12 UTCEPSS rescore
  33. 2026-06-11 22:09 UTCVendor advisory
  34. 2026-06-11 14:00 UTCEPSS rescore
  35. 2026-06-10 22:18 UTCEPSS rescore
  36. 2026-06-10 13:45 UTCVendor advisory
  37. 2026-06-10 13:22 UTCEPSS rescore
  38. 2026-06-10 01:45 UTCVendor advisory
  39. 2026-06-09 14:39 UTCVendor advisory
  40. 2026-06-08 14:17 UTCEPSS rescore
  41. 2026-06-08 14:17 UTCEPSS rescore
  42. 2026-06-08 09:23 UTCVendor advisory
  43. 2026-06-07 22:13 UTCVendor advisory
  44. 2026-06-07 15:25 UTCEPSS rescore
  45. 2026-06-07 15:25 UTCEPSS rescore
  46. 2026-06-07 15:25 UTCEPSS rescore
  47. 2026-06-07 11:02 UTCVendor advisory
  48. 2026-06-06 13:47 UTCEPSS rescore
  49. 2026-06-06 13:47 UTCEPSS rescore
  50. 2026-06-05 22:47 UTCEPSS rescore
  51. 2026-06-05 22:47 UTCEPSS rescore
  52. 2026-06-05 06:10 UTCEPSS rescore
  53. 2026-06-05 06:10 UTCEPSS rescore
  54. 2026-06-04 13:12 UTCEPSS rescore
  55. 2026-06-04 13:12 UTCEPSS rescore
  56. 2026-06-02 20:13 UTCEPSS rescore
  57. 2026-06-01 13:52 UTCEPSS rescore
  58. 2026-06-01 13:52 UTCEPSS rescore
  59. 2026-06-01 13:51 UTCEPSS rescore
  60. 2026-05-31 22:30 UTCEPSS rescore
  61. 2026-05-31 22:30 UTCEPSS rescore
  62. 2026-05-31 00:16 UTCEPSS rescore
  63. 2026-05-31 00:16 UTCEPSS rescore
  64. 2026-05-31 00:16 UTCEPSS rescore
  65. 2026-05-29 13:44 UTCEPSS rescore
  66. 2026-05-29 13:44 UTCEPSS rescore
  67. 2026-05-28 13:44 UTCEPSS rescore
  68. 2026-05-28 13:44 UTCEPSS rescore
  69. 2026-05-28 13:44 UTCEPSS rescore
  70. 2026-05-27 13:40 UTCEPSS rescore
  71. 2026-05-27 13:40 UTCEPSS rescore
  72. 2026-05-27 13:40 UTCEPSS rescore
  73. 2026-05-26 13:44 UTCEPSS rescore
  74. 2026-05-26 07:18 UTCEPSS rescore
  75. 2026-05-26 07:18 UTCEPSS rescore

Frequently asked(5)

What is CVE-2026-34742?
CVE-2026-34742 is a high vulnerability published on April 2, 2026. The Go MCP SDK used Go's standard encoding/json. Prior to version 1.4.0, the Model Context Protocol (MCP) Go SDK does not enable DNS rebinding protection by default for HTTP-based servers. When an HTTP-based MCP server is run on localhost without authentication with StreamableHTTPHandler or…
When was CVE-2026-34742 disclosed?
CVE-2026-34742 was first published in the National Vulnerability Database on April 2, 2026, with the most recent update on July 15, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-34742 actively exploited?
CVE-2026-34742 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 37.0% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-34742?
CVE-2026-34742 has a CVSS v3 base score of 8.1 (NVD).
How do I remediate CVE-2026-34742?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-34742, 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.

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