Improper Handling of Case Sensitivity Affecting gptscript package, versions <0.9.8-r35


Severity

Recommended
0.0
high
0
10

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Threat Intelligence

EPSS
0.05% (14th percentile)

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  • Snyk IDSNYK-WOLFILATEST-GPTSCRIPT-15447107
  • published10 Mar 2026
  • disclosed26 Feb 2026

Introduced: 26 Feb 2026

CVE-2026-27896  (opens in a new tab)
CWE-178  (opens in a new tab)
CWE-436  (opens in a new tab)

How to fix?

Upgrade Wolfi gptscript to version 0.9.8-r35 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream gptscript package and not the gptscript package as distributed by Wolfi. See How to fix? for Wolfi relevant fixed versions and status.

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.

CVSS Base Scores

version 3.1