CVE-2026-32112 — ha-mcp
MEDIUMCVE-2026-32112 is a medium-severity (CVSS 6.8) Cross-site Scripting (XSS) vulnerability in ha-mcp. A fix is available for ha-mcp — see the affected versions and patch details below.
ha-mcp has XSS via Unescaped HTML in OAuth Consent Form
Exploitation Status
No confirmed exploitation observed yet
- A successful exploit gives an attacker total control of the affected component, not partial access.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-32112.
EPSS Exploitation Probability
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.
How urgent is this, really
CVE-2026-32112 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 378,156 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
ha-mcpReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
Summary
The ha-mcp OAuth consent form renders user-controlled parameters via Python f-strings with no HTML escaping. An attacker who can reach the OAuth endpoint and convince the server operator to follow a crafted authorization URL could execute JavaScript in the operator's browser. This affects only users running the beta OAuth mode (ha-mcp-oauth), which is not part of the standard setup and requires explicit configuration.
Details
Unescaped f-string rendering
consent_form.py builds HTML using Python f-strings. No call to html.escape() exists anywhere in the file. The following values are rendered unescaped:
client_name/client_id— in HTML element context (lines 299, 303)client_id,redirect_uri,state— in HTML attribute context (lines 310–312), where a"character breaks out ofvalue=""error_message,error,error_description— in error display paths (lines 36–40, 496–497)
An attacker can register a client with a malicious client_name via the /register (DCR) endpoint, which accepts client_name without sanitization. If the server operator then visits a crafted authorization URL for that client, the payload executes in their browser.
Open Dynamic Client Registration
DCR is enabled by default with no initial access token required. This is intentional: Claude.ai and ChatGPT must self-register on first use, which is the standard MCP OAuth flow (RFC 7591). Requiring a pre-shared token would break those integrations. Registration alone grants no access — authorization requires an explicit action by the server operator.
Impact
Affected configuration: OAuth mode only (ha-mcp-oauth, requires MCP_BASE_URL). This mode is in beta and is not included in the main setup documentation. The vast majority of ha-mcp users run stdio mode, which is not affected.
Attack requirements:
- The attacker can reach the ha-mcp OAuth endpoint (it binds to
0.0.0.0in HTTP mode) - The attacker registers a malicious client via
/register - The attacker convinces the server operator — the person who set up ha-mcp — to follow a crafted authorization URL for an unrecognized application
Step 3 is a meaningful social engineering bar: the consent form displays the (unfamiliar) application name, and the operator has no legitimate reason to authorize an OAuth client they didn't initiate through Claude.ai or ChatGPT. Normal usage involves being redirected to the consent form from one of those platforms, not from an external link.
If exploited, a JavaScript payload could exfiltrate data entered into the consent form, including the Home Assistant Long-Lived Access Token.
Fix
Upgrade to 7.0.0
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | ha-mcp | all versions | 7.0.0pip install --upgrade 'ha-mcp==7.0.0' |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for ha-mcp, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update ha-mcp to 7.0.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-32112 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 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-32112 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-32112. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-32112 in your dependencies?
O3 Security finds CVE-2026-32112 across PyPI dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.