CVE
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.
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
- Exploited
- No known exploitation
- Fix
- Fixed in 0.0.70
- Who is exposed
- Specific setups only
Do first: Check whether your setup matches what the bug needs. The MCP fetch-tools endpoint is used with the sse or streamable_http transport, which fetch the attacker-supplied URL without a guard.
- Last modified
- Whether it needs action now or is a reference record, by fixed rules, with why. Last checked is when cve.now last re-read it.What do these mean? →
- Reference
- Last checked
- A 0-100 score for how much a CVE matters across the industry: exploitation, exposure, how widely the software is used, severity and whether a fix exists.What do these mean? →
- 15/100 · provisional
- How many real-world setups can hit the bug, from the vendor's advisory and CISA data. It does not know your setup.What do these mean? →
- Specific setups only
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
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.
Read the original 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.
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.
Read the source excerpt
“fetches an attacker-supplied URL through the sse and streamable_http transports”
cve.now Index
- Exploitation?/40Unknown. No CISA SSVC exploitation rating yet
- Exposure8/25Specific setups only, reachable over the network
- Reach?/20Unknown. No tracked technology or package matched
- Severity7.1/10CVSS 7.1
- No patch0/5No signal
What would change the score
- Would score about 65 if added to CISA KEV
- Would score about 60 if CISA's SSVC rates exploitation active
- Would score about 22 if CISA's SSVC rates it automatable
What to do
Check whether your setup matches what the bug needs.
The MCP fetch-tools endpoint is used with the sse or streamable_http transport, which fetch the attacker-supplied URL without a guard.Upgrade to a fixed version: 0.0.70.
Check your systems with an agent
Paste this into a coding or ops agent. It checks your systems read-only and reports a table per asset.
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"}.Timeline
- CVE published
- First seen by cve.now
Affected versions
- heymrun heym
fixed in 0.0.70
Evidence 5
Vendor advisory · 1
Establishes: Affected and fixed versions.
- Advisory
CVE record · 2
Establishes: The identifier and description.
- Record
- Record
Other links · 2
- Repository
- Repository
Corrections
None so far.
Something wrong on this page? Report an error. Every fix is listed here.
Questions about CVE-2026-67542
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: cve.now feed data
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: github.com
Which versions are affected by CVE-2026-67542?
heym: before 0.0.70.Source: cve.now feed data
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: github.com
How do I fix CVE-2026-67542?
Upgrade Heym to 0.0.70 or later.Source: github.com