CVE detail
CVE-2026-27896
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.
Buzz score
Why this CVE is surfacing
This all-time snapshot uses the same composite formula as Trending across a 30-year evidence window, rather than a current rolling window.
Buzz score components · mention 17.9 · diversity 13.0 · KEV 0.0 · OTX 0.0 · PoC 0.0
Why it matters now
Mention timeline
- Total mentions
- 0
- within the 30d window
- Peak daily
- 0
- highest bucket
Evidence
Source links by recency
5 source links · newest first
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-27896.jsonsecurity.access.redhat.com
No excerpt available.
Vendor Advisorysecurity.access.redhat.comFeb 26, 2026, 1:16 AM - https://bugzilla.redhat.com/show_bug.cgi?id=2442903bugzilla.redhat.com
No excerpt available.
Exploitbugzilla.redhat.comFeb 26, 2026, 1:16 AM - https://access.redhat.com/security/cve/CVE-2026-27896access.redhat.com
No excerpt available.
Exploitaccess.redhat.comFeb 26, 2026, 1:16 AM No excerpt available.
Exploitgithub.comFeb 26, 2026, 1:16 AM- https://github.com/modelcontextprotocol/go-sdk/commit/7b8d81c264074404abdf5aa16e2cf0c2d9c64cc0github.com
No excerpt available.
Exploitgithub.comFeb 26, 2026, 1:16 AM
Exploit code
Public exploit repository references
Public PoC repositories are third-party, potentially unsafe artifacts. Treat their code as untrusted and use it only on authorized systems in an isolated, least-privilege environment. cvebuzz does not execute the code or verify that an exploit works.
0 repository references · best confidence N/A · max 0 stars
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