How severe is GHSA-89xv-2j6f-qhc8?

GHSA-89xv-2j6f-qhc8 has a CVSS score of 7.1/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by GHSA-89xv-2j6f-qhc8?

GHSA-89xv-2j6f-qhc8 affects the following packages: github.com/modelcontextprotocol/go-sdk (Go). Ecosystems affected: Go.

How do I fix GHSA-89xv-2j6f-qhc8?

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-89xv-2j6f-qhc8 is resolved across your whole dependency graph.

How do I detect GHSA-89xv-2j6f-qhc8 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. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.

How do I mitigate GHSA-89xv-2j6f-qhc8 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.

How does O3 Security protect against GHSA-89xv-2j6f-qhc8?

O3 pinpoints whether GHSA-89xv-2j6f-qhc8 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Is GHSA-89xv-2j6f-qhc8 actively exploited in the wild?

No public exploit code has been indexed for GHSA-89xv-2j6f-qhc8 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.

What is the EPSS score for GHSA-89xv-2j6f-qhc8?

GHSA-89xv-2j6f-qhc8 has an EPSS (Exploit Prediction Scoring System) score of 0.2%, placing it in the 7th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is GHSA-89xv-2j6f-qhc8?

GHSA-89xv-2j6f-qhc8 is classified as Cross-Site Request Forgery (CSRF) (CWE-352). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was GHSA-89xv-2j6f-qhc8 published, and has it been updated?

GHSA-89xv-2j6f-qhc8 was published on March 19, 2026 and was last updated on March 25, 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

GHSA-89xv-2j6f-qhc8

HIGH

Cross-Site Tool Execution for HTTP Servers without Authorizatrion in github.com/modelcontextprotocol/go-sdk

Also known asCVE-2026-33252GO-2026-4773

Published

Mar 19, 2026

Updated

Mar 25, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

EPSS Exploitation Probability

via FIRST.org ↗

0.2%probability of exploitation in next 30 days

Lower Risk7th percentile+0.17%

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

Blast Radius

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's Streamable HTTP transport accepted browser-generated cross-site POST requests without validating the Origin header and without requiring Content-Type: application/json. In deployments without Authorization, especially stateless or sessionless configurations, this allows an arbitrary website to send MCP requests to a local server and potentially trigger tool execution.

Impact:

A malicious website may have been able to send cross-site POST requests with Content-Type: text/plain, which due to CORS-safelisted properties would reach the MCP message handling without any CORS preflight barrier.

Fix:

The SDK was modified to perform Content-Type header validation for POST requests and introduced a configurable protection for verifying the origin of the request in commit a433a83. Users are advised to update to v1.4.1 to use this additional protection.

Note: v1.4.1 requires Go 1.25 or later.

Credits:

Thank you to Lê Minh Quân for reporting the issue.

Affected Packages

1 total 1 fixed

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

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. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
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-89xv-2j6f-qhc8 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.
How O3 protects you
O3 pinpoints whether GHSA-89xv-2j6f-qhc8 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Tailored to GHSA-89xv-2j6f-qhc8. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

The Go SDK's Streamable HTTP transport accepted browser-generated cross-site `POST` requests without validating the `Origin` header and without requiring `Content-Type: application/json`. In deployments without Authorization, especially stateless or sessionless configurations, this allows an arbitrary website to send MCP requests to a local server and potentially trigger tool execution. #### Impact: A malicious website may have been able to send cross-site POST requests with `Content-Type: text/plain`, which due to CORS-safelisted properties would reach the MCP message handling without any C

O3 Security · Impact-Aware SCA

Is GHSA-89xv-2j6f-qhc8 in your dependencies?

O3 detects GHSA-89xv-2j6f-qhc8 across Go dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

Scan my dependencies How O3 SCA works