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CVE-2026-63118

MCP Ruby SDK is the official Ruby SDK for Model Context Protocol servers and clients. Prior to 0.23.0, MCP::Server::Transports::StreamableHTTPTransport in the mcp gem does not validate the HTTP Host or Origin request headers, which allows a malicious browser page to use DNS rebinding to reach a locally running MCP server and invoke exposed tools. This issue is fixed in version 0.23.0.
Lifecycle PUBLISHED1 preserved revisionFact urn:baitaphish:canonical-cve-fact-revision:v2:cbe1d0737d7f6a31837c285dfbc5e58d0b37ddfac23df900d1e0ed8e3dd99b12
Known exploited
Not asserted
Disputed
No
Stale source
No
Conflicts
1

Preserved source conflicts

No provider value was silently selected as the winner.

cwe · 2 assertions

{"cweId":"CWE-350","description":"CWE-350: Reliance on Reverse DNS Resolution for a Security-Critical Action","lang":"en","type":"CWE"}

  • cve_program_cvelist_v5cwe
    urn:baitaphish:normalized-source-record:v2:7f7a6abe1fbb073638fac07d07d6e31a0aa836d3095e395b6c62b057bfb5292c · sha256:76776066cbcab83a… · /containers/cna/problemTypes/1/descriptions/0

{"cweId":"CWE-346","description":"CWE-346: Origin Validation Error","lang":"en","type":"CWE"}

  • cve_program_cvelist_v5cwe
    urn:baitaphish:normalized-source-record:v2:7f7a6abe1fbb073638fac07d07d6e31a0aa836d3095e395b6c62b057bfb5292c · sha256:76776066cbcab83a… · /containers/cna/problemTypes/0/descriptions/0

Affected products and versions

1 source assertion
{"product":"ruby-sdk","vendor":"modelcontextprotocol","versions":[{"status":"affected","version":"< 0.23.0"}]}
  • cve_program_cvelist_v5affected
    urn:baitaphish:normalized-source-record:v2:7f7a6abe1fbb073638fac07d07d6e31a0aa836d3095e395b6c62b057bfb5292c · sha256:76776066cbcab83a… · /containers/cna/affected/0

Provider-owned CVSS observations

1 source assertion
{"metric":{"attackComplexity":"LOW","attackRequirements":"PRESENT","attackVector":"NETWORK","baseScore":6.9,"baseSeverity":"MEDIUM","privilegesRequired":"NONE","subAvailabilityImpact":"NONE","subConfidentialityImpact":"HIGH","subIntegrityImpact":"NONE","userInteraction":"ACTIVE","vectorString":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:H/VI:N/VA:N/SC:H/SI:N/SA:N","version":"4.0","vulnAvailabilityImpact":"NONE","vulnConfidentialityImpact":"HIGH","vulnIntegrityImpact":"NONE"},"metric_type":"cvssV4_0"}
  • cve_program_cvelist_v5cvss
    urn:baitaphish:normalized-source-record:v2:7f7a6abe1fbb073638fac07d07d6e31a0aa836d3095e395b6c62b057bfb5292c · sha256:76776066cbcab83a… · /containers/cna/metrics/0/cvssV4_0

CWE assertions

2 source assertions
{"cweId":"CWE-350","description":"CWE-350: Reliance on Reverse DNS Resolution for a Security-Critical Action","lang":"en","type":"CWE"}
  • cve_program_cvelist_v5cwe
    urn:baitaphish:normalized-source-record:v2:7f7a6abe1fbb073638fac07d07d6e31a0aa836d3095e395b6c62b057bfb5292c · sha256:76776066cbcab83a… · /containers/cna/problemTypes/1/descriptions/0
{"cweId":"CWE-346","description":"CWE-346: Origin Validation Error","lang":"en","type":"CWE"}
  • cve_program_cvelist_v5cwe
    urn:baitaphish:normalized-source-record:v2:7f7a6abe1fbb073638fac07d07d6e31a0aa836d3095e395b6c62b057bfb5292c · sha256:76776066cbcab83a… · /containers/cna/problemTypes/0/descriptions/0

Source references

4 source assertions
{"name":"https://github.com/modelcontextprotocol/ruby-sdk/commit/ba543083a7594e7892b29464b89091816446ff7a","tags":["x_refsource_MISC"],"url":"https://github.com/modelcontextprotocol/ruby-sdk/commit/ba543083a7594e7892b29464b89091816446ff7a"}
  • cve_program_cvelist_v5reference
    urn:baitaphish:normalized-source-record:v2:7f7a6abe1fbb073638fac07d07d6e31a0aa836d3095e395b6c62b057bfb5292c · sha256:76776066cbcab83a… · /containers/cna/references/1
{"name":"https://github.com/modelcontextprotocol/ruby-sdk/releases/tag/v0.23.0","tags":["x_refsource_MISC"],"url":"https://github.com/modelcontextprotocol/ruby-sdk/releases/tag/v0.23.0"}
  • cve_program_cvelist_v5reference
    urn:baitaphish:normalized-source-record:v2:7f7a6abe1fbb073638fac07d07d6e31a0aa836d3095e395b6c62b057bfb5292c · sha256:76776066cbcab83a… · /containers/cna/references/2
{"name":"https://github.com/modelcontextprotocol/ruby-sdk/security/advisories/GHSA-rjr6-rcgv-9m7m","tags":["x_refsource_CONFIRM"],"url":"https://github.com/modelcontextprotocol/ruby-sdk/security/advisories/GHSA-rjr6-rcgv-9m7m"}
  • cve_program_cvelist_v5reference
    urn:baitaphish:normalized-source-record:v2:7f7a6abe1fbb073638fac07d07d6e31a0aa836d3095e395b6c62b057bfb5292c · sha256:76776066cbcab83a… · /containers/cna/references/0
{"tags":["exploit"],"url":"https://github.com/modelcontextprotocol/ruby-sdk/security/advisories/GHSA-rjr6-rcgv-9m7m"}
  • cve_program_cvelist_v5reference
    urn:baitaphish:normalized-source-record:v2:7f7a6abe1fbb073638fac07d07d6e31a0aa836d3095e395b6c62b057bfb5292c · sha256:76776066cbcab83a… · /containers/adp/0/references/0

Attribution and limitations

  • CVE Program CVEList V5: Reproduce the MITRE copyright designation and CVE license in copies. Source →

Provider severity values are preserved separately. Baitaphish does not convert them into a risk rating, infer affected products, or treat EPSS as observed exploitation.

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