{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-27896", "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa", "state": "PUBLISHED", "assignerShortName": "GitHub_M", "dateReserved": "2026-02-24T15:19:29.717Z", "datePublished": "2026-02-26T00:47:46.967Z", "dateUpdated": "2026-07-15T01:12:30.910Z" }, "containers": { "cna": { "title": "MCP Go SDK Vulnerable to Improper Handling of Case Sensitivity", "problemTypes": [ { "descriptions": [ { "cweId": "CWE-178", "lang": "en", "description": "CWE-178: Improper Handling of Case Sensitivity", "type": "CWE" } ] }, { "descriptions": [ { "cweId": "CWE-436", "lang": "en", "description": "CWE-436: Interpretation Conflict", "type": "CWE" } ] } ], "metrics": [ { "cvssV4_0": { "attackVector": "NETWORK", "attackComplexity": "LOW", "attackRequirements": "PRESENT", "privilegesRequired": "NONE", "userInteraction": "NONE", "vulnConfidentialityImpact": "NONE", "vulnIntegrityImpact": "NONE", "vulnAvailabilityImpact": "NONE", "subConfidentialityImpact": "HIGH", "subIntegrityImpact": "HIGH", "subAvailabilityImpact": "NONE", "baseScore": 7, "baseSeverity": "HIGH", "vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N", "version": "4.0" } } ], "references": [ { "name": "https://github.com/modelcontextprotocol/go-sdk/security/advisories/GHSA-wvj2-96wp-fq3f", "tags": [ "x_refsource_CONFIRM" ], "url": "https://github.com/modelcontextprotocol/go-sdk/security/advisories/GHSA-wvj2-96wp-fq3f" }, { "name": "https://github.com/modelcontextprotocol/go-sdk/commit/7b8d81c264074404abdf5aa16e2cf0c2d9c64cc0", "tags": [ "x_refsource_MISC" ], "url": "https://github.com/modelcontextprotocol/go-sdk/commit/7b8d81c264074404abdf5aa16e2cf0c2d9c64cc0" } ], "affected": [ { "vendor": "modelcontextprotocol", "product": "go-sdk", "versions": [ { "version": "< 1.3.1", "status": "affected" } ] } ], "providerMetadata": { "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa", "shortName": "GitHub_M", "dateUpdated": "2026-02-26T00:47:46.967Z" }, "descriptions": [ { "lang": "en", "value": "The Go MCP SDK used Go's standard encoding/json.Unmarshal for JSON-RPC and MCP protocol message parsing in versions prior to 1.3.1. Go's standard library performs case-insensitive matching of JSON keys to struct field tags — a field tagged json:\"method\" would also match \"Method\", \"METHOD\", etc. This violated the JSON-RPC 2.0 specification, which defines exact field names. A malicious MCP peer may have been able to send protocol messages with non-standard field casing that the SDK would silently accept. This had the potential for bypassing intermediary inspection and coss-implementation inconsistency. Go's standard JSON unmarshaling was replaced with a case-sensitive decoder in commit 7b8d81c. Users are advised to update to v1.3.1 to resolve this issue." } ], "source": { "advisory": "GHSA-wvj2-96wp-fq3f", "discovery": "UNKNOWN" } }, "adp": [ { "metrics": [ { "other": { "type": "ssvc", "content": { "timestamp": "2026-02-26T17:06:14.973622Z", "id": "CVE-2026-27896", "options": [ { "Exploitation": "none" }, { "Automatable": "yes" }, { "Technical Impact": "partial" } ], "role": "CISA Coordinator", "version": "2.0.3" } } } ], "title": "CISA ADP Vulnrichment", "providerMetadata": { "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-02-26T17:06:41.150Z" } }, { "affected": [ { "collectionURL": "https://access.redhat.com/downloads/content/package-browser/", "cpes": [ "cpe:/a:redhat:migration_toolkit_virtualization:2" ], "defaultStatus": "affected", "packageName": "migration-toolkit-virtualization/mtv-cli-download-rhel9", "product": "Migration Toolkit for Virtualization", "vendor": "Red Hat" }, { "collectionURL": "https://access.redhat.com/downloads/content/package-browser/", "cpes": [ "cpe:/a:redhat:migration_toolkit_virtualization:2" ], "defaultStatus": "affected", "packageName": "mtv-candidate/mtv-api-rhel9", "product": "Migration Toolkit for Virtualization", "vendor": "Red Hat" }, { "collectionURL": "https://access.redhat.com/downloads/content/package-browser/", "cpes": [ "cpe:/a:redhat:migration_toolkit_virtualization:2" ], "defaultStatus": "affected", "packageName": "mtv-candidate/mtv-cli-download-rhel9", "product": "Migration Toolkit for Virtualization", "vendor": "Red Hat" }, { "collectionURL": "https://access.redhat.com/downloads/content/package-browser/", "cpes": [ "cpe:/a:redhat:migration_toolkit_virtualization:2" ], "defaultStatus": "affected", "packageName": "mtv-candidate/mtv-controller-rhel9", "product": "Migration Toolkit for Virtualization", "vendor": "Red Hat" }, { "collectionURL": "https://access.redhat.com/downloads/content/package-browser/", "cpes": [ "cpe:/a:redhat:migration_toolkit_virtualization:2" ], "defaultStatus": "affected", "packageName": "mtv-candidate/mtv-operator-bundle", "product": "Migration Toolkit for Virtualization", "vendor": "Red Hat" }, { "collectionURL": "https://access.redhat.com/downloads/content/package-browser/", "cpes": [ "cpe:/a:redhat:openshift_lightspeed" ], "defaultStatus": "affected", "packageName": "openshift-lightspeed/openshift-mcp-server-rhel9", "product": "OpenShift Lightspeed", "vendor": "Red Hat" }, { "collectionURL": "https://access.redhat.com/downloads/content/package-browser/", "cpes": [ "cpe:/a:redhat:serverless:1" ], "defaultStatus": "affected", "packageName": "openshift-serverless-1/kn-client-kn-rhel9", "product": "OpenShift Serverless", "vendor": "Red Hat" }, { "collectionURL": "https://access.redhat.com/downloads/content/package-browser/", "cpes": [ "cpe:/a:redhat:serverless:1" ], "defaultStatus": "affected", "packageName": "openshift-serverless-1/kn-plugin-func-func-util-rhel9", "product": "OpenShift Serverless", "vendor": "Red Hat" }, { "collectionURL": "https://access.redhat.com/downloads/content/package-browser/", "cpes": [ "cpe:/a:redhat:openshift_ai" ], "defaultStatus": "affected", "packageName": "rhoai/odh-dashboard-rhel9", "product": "Red Hat OpenShift AI (RHOAI)", "vendor": "Red Hat" }, { "collectionURL": "https://access.redhat.com/downloads/content/package-browser/", "cpes": [ "cpe:/a:redhat:openshift_ai" ], "defaultStatus": "affected", "packageName": "rhoai/odh-mod-arch-gen-ai-rhel9", "product": "Red Hat OpenShift AI (RHOAI)", "vendor": "Red Hat" }, { "collectionURL": "https://access.redhat.com/downloads/content/package-browser/", "cpes": [ "cpe:/a:redhat:openshift_ai" ], "defaultStatus": "affected", "packageName": "rhoai/odh-mod-arch-model-registry-rhel9", "product": "Red Hat OpenShift AI (RHOAI)", "vendor": "Red Hat" } ], "datePublic": "2026-02-26T00:47:46.967Z", "descriptions": [ { "lang": "en", "value": "A flaw was found in the Go MCP SDK. This issue occurs due to an improper handling of case sensitivity during JSON-RPC message parsing, specifically in the matching of JSON keys to struct field tags. This behavior violates the JSON-RPC 2.0 specification, which explicitly requires case-sensitive field name matching. A malicious MCP peer able to send protocol messages with non-standard field casing can potentially bypass intermediary inspection, allowing attackers to smuggle payloads past upstream filters and cause cross-implementation inconsistency." } ], "metrics": [ { "other": { "content": { "namespace": "https://access.redhat.com/security/updates/classification/", "value": "Important" }, "type": "Red Hat severity rating" } }, { "cvssV3_1": { "attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "NONE", "baseScore": 7.2, "baseSeverity": "HIGH", "confidentialityImpact": "LOW", "integrityImpact": "LOW", "privilegesRequired": "NONE", "scope": "CHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N", "version": "3.1" }, "format": "CVSS" } ], "problemTypes": [ { "descriptions": [ { "cweId": "CWE-178", "description": "Improper Handling of Case Sensitivity", "lang": "en", "type": "CWE" } ] } ], "references": [ { "tags": [ "vdb-entry", "x_refsource_REDHAT" ], "url": "https://access.redhat.com/security/cve/CVE-2026-27896" }, { "name": "RHBZ#2442903", "tags": [ "issue-tracking", "x_refsource_REDHAT" ], "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2442903" }, { "tags": [ "x_sadp-csaf-vex" ], "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-27896.json" } ], "timeline": [ { "lang": "en", "time": "2026-02-26T01:01:38.878Z", "value": "Reported to Red Hat." }, { "lang": "en", "time": "2026-02-26T00:47:46.967Z", "value": "Made public." } ], "title": "modelcontextprotocol/go-sdk: improper handling of case sensitivity", "workarounds": [ { "lang": "en", "value": "To mitigate this flaw, strictly enforce JSON-RPC case sensitivity before payload processing or harden upstream WAF and proxy rules to explicitly block improperly cased requests at the network edge." } ], "x_adpType": "supplier", "x_generator": { "engine": "sadp-cli 1.0.0" }, "providerMetadata": { "orgId": "0b0ca135-0b70-47e7-9f44-1890c2a1c46c", "shortName": "redhat-SADP", "dateUpdated": "2026-07-15T01:12:30.910Z" } } ] } }