CVE-2026-27896
HIGHDescription
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.
How to fix
TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works
Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.
CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Exploit Intelligence
Low risk: more likely to be exploited than 17% of all known CVEs.
References
Related Vulnerabilities
Other CWE-178 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2025-27636 | Medium | 5.6 | 80% | - | Fix |
| CVE-2021-24347 | High | 8.8 | 52% | - | Fix |
| CVE-2020-12812 | Critical | 9.8 | 49% | KEV + Ransom | Fix |
| CVE-2003-0411 | High | 7.5 | 25% | - | - |
| CVE-2018-9845 | Critical | 9.8 | 13% | - | Fix |
| CVE-2001-0766 | Critical | 9.8 | 8.2% | - | - |
Embed a live status badge for CVE-2026-27896
Markdown
[](https://tridentstack.com/cve/CVE-2026-27896)HTML
<a href="https://tridentstack.com/cve/CVE-2026-27896"><img src="https://tridentstack.com/cve/badge/CVE-2026-27896.svg" alt="CVE-2026-27896"></a>Find and fix vulnerabilities across your fleet
TridentStack Control continuously scans your Windows, macOS, and Linux fleet for known vulnerabilities, prioritizes them by severity and active exploitation, and patches them automatically.
This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-07-15.