CVE-2026-27896High· 7.2▾ TwilightA 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 …
▾ Twilight zone — High severity, or a signal on a lesser flaw
impact 39.6 · likelihood 0.1 · exploitation 0
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Stakeholder-Specific Vulnerability Categorization from CISA's ADP record at CVE.org: whether exploitation is observed, whether an attack can be automated, and how much of the system is at stake. The CVSS score shown above comes from the vendor's CSAF advisory record, not NVD.
Exploit-prediction probability, daily snapshots since Sep 16.
Disclosure to exploitation, from the record and what we observed since indexing it.
Disclosed via CSAF
0.3%
Last analysed / modified upstream
7 → 7.2
0.3% → 0.5%
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.
modelcontextprotocol/go-sdk: improper handling of case sensitivity — rated Important by Red Hat. Released 2026-02-26, updated 2026-10-15.
Affected:
No fix planned:
Will not fix
Workarounds / mitigations:
Field changes observed since this record was first indexed.
Connected by shared product, vendor, weakness, or advisory.
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