CVE-2026-34742

HIGHNVD 8.18.1
EchelonGraph scoreMEDIUM confidence

“—” beside the score: it is equal to NVD's CVSS score.

Score 8.1 from GitHub Security Advisory (severity: HIGH) published 2026-04-01. NVD baseline CVSS 8.1; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: EPSS, GitHub Security Advisory, NVD CVSS v3
Trending — 4 sources updated this week

Also known asEUVD-2026-18503 (ENISA EUVD) · GHSA-xw59-hvm2-8pj6 (GitHub Security Advisories)Source: ENISA EUVD

8.1EG
EchelonGraph verdictPlan a fixRemediate within your standard update timelines (the SSVC decision on this page).
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0.5%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 impact severity (EG Severity, the CVSS base score, never the KEV-floored or EPSS-lifted EG Score) with real-world exploitation and automatability, under weights EchelonGraph set by hand, so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner.

How it’s computed (value × EchelonGraph’s weight)
Severity81% × 45%
Impact severity (EG Severity): CVSS 8.1 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation0.5% × 40%
FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.
Automatability0% × 15%
CISA's SSVC Automatable value: no (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at low or medium mission impact; Track* at high (mission-essential systems).
Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.
Action: A fix is available. Apply it within your standard update timelines.
EPSS PROB
0.5%
EPSS %ILE
40th
KEV
Not listed

What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)

The EG score (8.1): severity, escalated by confirmed exploitation. This CVE's 8.1 is its impact severity (EG Severity), not escalated.

EG Severity
8.1 HIGHCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
EG Likelihood
0.5% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-31). FIRST's exploitation probability, not an EchelonGraph model.
Confirmed exploitation
None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
EG Priority
SSVC Track at medium mission impactTrack at low or medium mission impact; Track* at high (mission-essential systems).CISA BOD 26-04: 14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.Each input and its source, and whom BOD 26-04 binds: the SSVC and BOD 26-04 blocks below.

SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Track* at high (mission-essential systems).

A fix is available. Apply it within your standard update timelines.

Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table

BOD 26-04 (CISA's remediation timeline, Table 1)14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.

The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it

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.
GitHub advisoryMentions 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 pull request 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(2)

Vendor / EcosystemFix (by version range) / PatchReleasedSource
redhatdevspaces/udi-rhel9:17798297362026-05-28redhat
gogithub.com/modelcontextprotocol/go-sdk @ 1.4.0 (fixes < 1.4.0)—ghsa

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 10× in last 7d / 44× in last 30d)

Each row is a time one of our pipelines fetched, updated or re-scored this CVE. 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. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.

Showing the most recent 99 of 245 refreshes on record for this CVE.

A repeat, a row identical to one the same pipeline wrote less than 10 seconds earlier, is not a separate refresh and is not counted. 1 repeat row among the latest 100 is merged into the row it repeats. The 146 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-11-02 16:44 UTCEPSS rescoreEPSS 0.5% · 40th percentile
  2. 2026-11-01 16:34 UTCEPSS rescoreEPSS 0.5% · 40th percentile
  3. 2026-11-01 07:53 UTCGHSA enrichmentGHSA-xw59-hvm2-8pj6 · GitHub severity HIGH · GitHub CVSS 8.1
  4. 2026-11-01 07:53 UTCEG score recompute
  5. 2026-10-31 11:45 UTCEG score recompute
  6. 2026-10-31 11:45 UTCVendor advisory
  7. 2026-10-30 16:34 UTCEPSS rescoreEPSS 0.5% · 40th percentile
  8. 2026-10-29 16:33 UTCEPSS rescoreEPSS 0.5% · 39th percentile
  9. 2026-10-28 16:32 UTCEPSS rescoreEPSS 0.5% · 39th percentile
  10. 2026-10-27 16:31 UTCEPSS rescoreEPSS 0.5% · 39th percentile
  11. 2026-10-26 16:31 UTCEPSS rescoreEPSS 0.5% · 39th percentile
  12. 2026-10-25 16:32 UTCEPSS rescoreEPSS 0.5% · 39th percentile
  13. 2026-10-25 14:33 UTCEG score recompute
  14. 2026-10-24 16:32 UTCEPSS rescoreEPSS 0.7% · 51st percentile
  15. 2026-10-24 13:39 UTCEG score recompute
  16. 2026-10-24 13:39 UTCVendor advisory
  17. 2026-10-23 16:31 UTCEPSS rescoreEPSS 0.7% · 51st percentile
  18. 2026-10-22 16:34 UTCEPSS rescoreEPSS 0.7% · 51st percentile
  19. 2026-10-21 16:33 UTCEPSS rescoreEPSS 0.7% · 51st percentile
  20. 2026-10-20 16:33 UTCEPSS rescoreEPSS 0.7% · 50th percentile
  21. 2026-10-19 16:31 UTCEPSS rescoreEPSS 0.7% · 50th percentile
  22. 2026-10-18 16:31 UTCEPSS rescoreEPSS 0.7% · 50th percentile
  23. 2026-10-18 03:45 UTCEG score recompute
  24. 2026-10-17 16:34 UTCEPSS rescoreEPSS 0.7% · 50th percentile
  25. 2026-10-17 15:29 UTCEG score recompute
Show 74 more
  1. 2026-10-17 15:29 UTCVendor advisory
  2. 2026-10-16 16:41 UTCEPSS rescoreEPSS 0.7% · 50th percentile
  3. 2026-10-15 16:32 UTCEPSS rescoreEPSS 0.7% · 50th percentile
  4. 2026-10-14 16:32 UTCEPSS rescoreEPSS 0.7% · 50th percentile
  5. 2026-10-13 16:34 UTCEPSS rescoreEPSS 0.7% · 50th percentile
  6. 2026-10-12 16:34 UTCEPSS rescoreEPSS 0.7% · 50th percentile
  7. 2026-10-12 16:12 UTCEG score recompute
  8. 2026-10-11 19:54 UTCEG score recompute
  9. 2026-10-11 17:07 UTCEG score recompute
  10. 2026-10-11 14:34 UTCEG score recompute
  11. 2026-10-11 13:48 UTCEPSS rescoreEPSS 0.7% · 50th percentile
  12. 2026-10-11 02:31 UTCOSV refresh
  13. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.7% · 50th percentile
  14. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.7% · 50th percentile
  15. 2026-10-08 17:12 UTCEPSS rescoreEPSS 0.7% · 50th percentile
  16. 2026-10-07 23:47 UTCEPSS rescoreEPSS 0.7% · 50th percentile
  17. 2026-10-06 15:17 UTCEPSS rescoreEPSS 0.7% · 50th percentile
  18. 2026-10-05 17:42 UTCEPSS rescoreEPSS 0.7% · 50th percentile
  19. 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.7% · 49th percentile
  20. 2026-10-03 14:25 UTCEPSS rescoreEPSS 0.7% · 49th percentile
  21. 2026-10-01 19:49 UTCEPSS rescoreEPSS 0.7% · 49th percentile
  22. 2026-09-30 15:03 UTCEPSS rescoreEPSS 0.7% · 49th percentile
  23. 2026-09-28 13:51 UTCEPSS rescoreEPSS 0.7% · 49th percentile
  24. 2026-09-27 13:48 UTCEPSS rescoreEPSS 0.7% · 49th percentile
  25. 2026-09-26 15:58 UTCEPSS rescoreEPSS 0.7% · 49th percentile
  26. 2026-09-26 00:26 UTCEPSS rescoreEPSS 0.7% · 49th percentile
  27. 2026-09-21 13:49 UTCOSV refresh
  28. 2026-09-18 19:28 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  29. 2026-09-17 19:30 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  30. 2026-09-16 14:08 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  31. 2026-09-16 05:15 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  32. 2026-09-15 03:11 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  33. 2026-09-13 16:47 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  34. 2026-09-12 15:01 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  35. 2026-09-11 14:53 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  36. 2026-09-11 09:37 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  37. 2026-09-10 09:34 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  38. 2026-09-08 22:00 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  39. 2026-09-07 16:01 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  40. 2026-09-06 13:47 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  41. 2026-09-04 05:06 UTCEPSS rescoreEPSS 0.5% · 37th percentile
  42. 2026-09-02 14:12 UTCEPSS rescoreEPSS 0.5% · 37th percentile
  43. 2026-09-02 11:14 UTCOSV refresh
  44. 2026-09-01 13:53 UTCEPSS rescoreEPSS 0.5% · 37th percentile
  45. 2026-09-01 04:39 UTCEPSS rescoreEPSS 0.5% · 37th percentile
  46. 2026-08-30 19:17 UTCEPSS rescoreEPSS 0.5% · 37th percentile
  47. 2026-08-30 01:22 UTCEPSS rescoreEPSS 0.5% · 37th percentile
  48. 2026-08-28 21:41 UTCEPSS rescoreEPSS 0.5% · 37th percentile
  49. 2026-08-27 14:25 UTCEPSS rescoreEPSS 0.5% · 37th percentile
  50. 2026-08-26 14:46 UTCEPSS rescoreEPSS 0.5% · 37th percentile
  51. 2026-08-25 13:49 UTCEPSS rescoreEPSS 0.5% · 37th percentile
  52. 2026-08-23 00:19 UTCEPSS rescoreEPSS 0.5% · 37th percentile
  53. 2026-08-21 23:49 UTCEPSS rescoreEPSS 0.5% · 37th percentile
  54. 2026-08-20 22:55 UTCEPSS rescoreEPSS 0.5% · 37th percentile
  55. 2026-08-19 17:03 UTCEPSS rescoreEPSS 0.5% · 37th percentile
  56. 2026-08-18 13:48 UTCEPSS rescoreEPSS 0.5% · 37th percentile
  57. 2026-08-17 13:47 UTCEPSS rescoreEPSS 0.5% · 37th percentile
  58. 2026-08-16 14:56 UTCEPSS rescoreEPSS 0.5% · 37th percentile
  59. 2026-08-16 09:20 UTCEG score recompute
  60. 2026-08-16 09:20 UTCVendor advisory
  61. 2026-08-16 02:14 UTCEPSS rescoreEPSS 0.5% · 37th percentile
  62. 2026-08-15 01:30 UTCEPSS rescoreEPSS 0.5% · 37th percentile
  63. 2026-08-14 18:53 UTCVendor advisory
  64. 2026-08-14 05:46 UTCEG score recompute
  65. 2026-08-14 05:46 UTCVendor advisory
  66. 2026-08-13 22:00 UTCEPSS rescoreEPSS 0.5% · 37th percentile
  67. 2026-08-13 09:57 UTCVendor advisory
  68. 2026-08-12 20:00 UTCEG score recompute
  69. 2026-08-12 20:00 UTCVendor advisory
  70. 2026-08-12 13:50 UTCEPSS rescoreEPSS 0.5% · 37th percentile
  71. 2026-08-11 20:27 UTCEG score recompute
  72. 2026-08-11 20:27 UTCVendor advisory
  73. 2026-08-11 03:28 UTCEG score recompute
  74. 2026-08-11 03:28 UTCVendor advisory

Frequently asked(5)

What is CVE-2026-34742?
CVE-2026-34742 is a high-severity vulnerability; its CVE record was 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 the CVE record for CVE-2026-34742 published?
The CVE record for CVE-2026-34742 was published on April 2, 2026. That is the record's publication date; the vulnerability itself may have been made public earlier. EchelonGraph's copy of the record carries a last-modified date of July 24, 2026; the record at its source may have been updated since.
Is CVE-2026-34742 actively exploited?
CVE-2026-34742 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.5% probability of exploitation in the next 30 days (40th 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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