Description
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.
INFO
Published Date :
2026-02-26T00:47:46.967Z
Last Modified :
2026-02-26T17:06:41.150Z
Source :
GitHub_M
AFFECTED PRODUCTS
The following products are affected by CVE-2026-27896 vulnerability.
| Vendors | Products |
|---|---|
| Lfprojects |
|
| Modelcontextprotocol |
|
REFERENCES
Here, you will find a curated list of external links that provide in-depth information to CVE-2026-27896.
