# CVE-2026-35577: Missing Host Header Validation in Apollo MCP Server for Localhost Deployments

> Attackers can bypass same-origin policy via DNS rebinding to invoke tools on local Apollo MCP servers lacking Host header validation.

- **Severity:** Medium 6.8 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 9 Apr 2026
- **Updated:** 13 Apr 2026
- **Also known as:** GHSA-wqrj-vp8w-f8vh

## What is CVE-2026-35577?

CVE-2026-35577 is a medium-severity vulnerability in apollographql apollo-mcp-server, published on 9 Apr 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

Apollo MCP Server is a Model Context Protocol server that exposes GraphQL operations as MCP tools. Prior to version 1.7.0, the Apollo MCP Server did not validate the Host header on incoming HTTP requests when using StreamableHTTP transport. In configurations where an HTTP-based MCP server is run on localhost without additional authentication or network-level controls, this could potentially allow a malicious website—visited by a user running the server locally—to use DNS rebinding techniques to bypass same-origin policy restrictions and issue requests to the local MCP server. If successfully exploited, this could allow an attacker to invoke tools or access resources exposed by the MCP server on behalf of the local user. This issue is limited to HTTP-based transport modes (StreamableHTTP). It does not affect servers using stdio transport. The practical risk is further reduced in deployments that use authentication, network-level access controls, or are not bound to localhost. This vulnerability is fixed in 1.7.0.

Weakness: CWE-346 (Origin Validation Error)

## Which versions are affected by CVE-2026-35577?

It affects 1 product.


Products: Apollographql Apollo Mcp Server.

## How do I fix CVE-2026-35577?

No fix has been published for CVE-2026-35577 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-35577 being exploited?

There is no known exploitation of CVE-2026-35577 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-35577 and fix it if it is affected.

What it is: CVE-2026-35577 is a medium-severity vulnerability in apollographql apollo-mcp-server, published on 9 Apr 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-35577 in the wild and no public exploit code.

Affected product: apollographql apollo-mcp-server. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-35577/ (Markdown: https://insights.sbomify.com/CVE-2026-35577/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-35577
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-35577
- OSV: https://osv.dev/vulnerability/CVE-2026-35577

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-35577/
Summaries are generated and may contain mistakes; the official description above is the record.