How severe is GHSA-q382-vc8q-7jhj?

No CVSS score has been assigned to GHSA-q382-vc8q-7jhj yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by GHSA-q382-vc8q-7jhj?

GHSA-q382-vc8q-7jhj affects the following packages: github.com/modelcontextprotocol/go-sdk (Go). Ecosystems affected: Go.

How do I fix GHSA-q382-vc8q-7jhj?

Update github.com/modelcontextprotocol/go-sdk to 1.4.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-q382-vc8q-7jhj is resolved across your whole dependency graph.

How do I detect GHSA-q382-vc8q-7jhj in my Go dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/modelcontextprotocol/go-sdk, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate GHSA-q382-vc8q-7jhj if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Is GHSA-q382-vc8q-7jhj actively exploited in the wild?

No public exploit code has been indexed for GHSA-q382-vc8q-7jhj yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

When was GHSA-q382-vc8q-7jhj published, and has it been updated?

GHSA-q382-vc8q-7jhj was published on March 19, 2026 and was last updated on September 10, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐹 Go

Not in CISA KEV

Improper handling of null Unicode character when parsing JSON in github.com/modelcontextprotocol/go-sdkGHSA-q382-vc8q-7jhj

Fix: modelcontextprotocol/go-sdk@724dd47

GHSA-q382-vc8q-7jhj is a security vulnerability in github.com/modelcontextprotocol/go-sdk. A fix is available for github.com/modelcontextprotocol/go-sdk — see the affected versions and patch details below.

Also known asGO-2026-4770

Published

Mar 19, 2026

Updated

Sep 10, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Sep 10, 2026 · OSV.dev, FIRST.org (EPSS)

Real-World Exposure

1 pkg affected

🐹github.com/modelcontextprotocol/go-sdk

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.

Description

The Go SDK recently transitioned to the segmentio/encoding library for JSON parsing in version 1.3.1. While this change addressed both case-insensitivity and ASCII folding issues, the new parser implemented aggressive key matching that treated keys with null Unicode characters appended at the end as equivalent to their base strings.

Impact

When combined with duplicate keys, the described behavior leads to a "last key wins" resolution that could override the intended MCP message. This had the potential for:

Bypassing intermediary inspection: Proxies or policy layers that matched on exact field names may have failed to detect or filter these messages.
Cross-implementation inconsistency: Other MCP SDKs (TypeScript, Python) use case-sensitive parsing and would reject the same messages, creating potential security-boundary confusion.

Fix:

The segmentio/encoding package was patched with a fix in https://github.com/segmentio/encoding/commit/7d5a25dbc5da13aed3cb047a127e4d0e96f536fb and a new version of the package was released (v0.5.4). The SDK switched to the patched version of the dependency in 724dd47aa. Users are advised to update to v1.4.1 to resolve this issue.

Credits:

Thank you to Francesco Lacerenza (Doyensec) for reporting this issue.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐹Go	`github.com/modelcontextprotocol/go-sdk`	all versions	1.4.1`go get github.com/modelcontextprotocol/go-sdk@v1.4.1`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/modelcontextprotocol/go-sdk, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/modelcontextprotocol/go-sdk to 1.4.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-q382-vc8q-7jhj is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

The Go SDK recently transitioned to the `segmentio/encoding` library for JSON parsing in version 1.3.1. While this change addressed both case-insensitivity and ASCII folding issues, the new parser implemented aggressive key matching that treated keys with `null` Unicode characters appended at the end as equivalent to their base strings. #### Impact When combined with duplicate keys, the described behavior leads to a "last key wins" resolution that could override the intended MCP message. This had the potential for: - **Bypassing intermediary inspection:** Proxies or policy layers that matc

O3 Security · Impact-Aware SCA

Is GHSA-q382-vc8q-7jhj in your dependencies?

Find it across Go, including transitive dependencies.

Scan my dependencies How O3 SCA works