CVE-2026-34742

HIGHNVD 8.18.1—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 8.1 under NVD CVSS v3. EPSS exploit probability: 0.5%, top 62% 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
8.1EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0.7%CVSS: 8.1Exploit: None knownExposed services: Not assessed

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
8.1HIGHmedium confidence
EG Risk
37
EG Risk 37/100

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
Severity81% × 45%
Exploitation0% × 40%
Automatability0% × 15%
EPSS PROB
0.7%
EPSS %ILE
50th
KEV
Not listed

Published

April 2, 2026

Last Modified

July 24, 2026

Advisory Details (4)

Auto-updated Jun 10, 2026
Patch available. Sources: github, github_commit, github_pr, github_release.
githubMentions a patch (unverified)

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 / EcosystemFix (by version range) / 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 rangeFix by version rangeDependents
github.com/modelcontextprotocol/go-sdk—
  • every version up to 1.4.0: fixed in 1.4.0
—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 7× in last 7d / 25× 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 209 total refreshes for this CVE.

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

Related CVEs(same product + same vendor + same CWE)

Same product

2 shown

Go:github.com/modelcontextprotocol/go-sdk

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 on April 2, 2026, with the most recent update on July 24, 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 0.7% probability of exploitation in the next 30 days (50th percentile of EPSS-scored CVEs).
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?
A fix for CVE-2026-34742 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-34742 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

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