{"id":"CVE-2026-67546","kind":"vulnerability","aliases":["CVE-2026-67546"],"related":[],"title":"Heym: any logged-in user can run commands on the server","description":"Heym builds and runs agentic systems and business-process automations on self-hosted infrastructure. Prior to version 0.0.75, the same POST /api/mcp/fetch-tools endpoint (any authenticated user, lowest role) also accepts the stdio transport, which spawns the attacker-supplied command with attacker-supplied args and an environment merged over os.environ. The process executes on the shared backend host before MCP protocol validation fails — so side effects fire regardless of whether the command speaks MCP. This is a distinct weakness class and exploit primitive from the SSRF (Advisory 2) on the same endpoint, and needs a different fix (role gating / opt-in trust boundary rather than egress controls). This issue has been patched in version 0.0.75.","summary":"Heym's MCP fetch-tools endpoint accepts the stdio transport, which spawns an attacker-supplied command with attacker-supplied arguments and environment on the backend host. Any authenticated user, including the lowest role, can execute code on the shared server before MCP validation fails.","severity":"high","cvss":8.8,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["ai-tooling","heym","mcp","self-hosted"],"not_affected_if":["version-0.0.75-or-later"],"how_to_check":"- Check the installed Heym version and confirm it is below `0.0.75`\n- Review whether POST /api/mcp/fetch-tools is reachable by ordinary authenticated users","fix":"- Heym: upgrade to `0.0.75` or later","status":"open","published_at":"2026-11-11T22:17:29+00:00","first_seen_at":"2026-11-11T22:29:35+00:00","triaged_at":"2026-11-11T22:31:14+00:00","updated_at":"2026-11-11T22:31:14+00:00","category":"ai-tooling","confidence":0.8,"triage":{"at":"2026-11-11T22:31:14Z","model":"claude-haiku-5-5","output":{"fix":"- Heym: upgrade to `0.0.75` or later","reach":"network","title":"Heym: any logged-in user can run commands on the server","impact":"high","summary":"Heym's MCP fetch-tools endpoint accepts the stdio transport, which spawns an attacker-supplied command with attacker-supplied arguments and environment on the backend host. Any authenticated user, including the lowest role, can execute code on the shared server before MCP validation fails.","audience":"businesses","category":"ai-tooling","nicknames":[],"who_cares":["heym","self-hosted","mcp"],"confidence":0.8,"fix_status":"available","needs_auth":"yes","worst_case":"code runs on the shared backend host as the server process","analyst_note":"","how_to_check":"- Check the installed Heym version and confirm it is below `0.0.75`\n- Review whether POST /api/mcp/fetch-tools is reachable by ordinary authenticated users","plain_action":"","product_name":"","needs_analyst":false,"not_affected_if":["version-0.0.75-or-later"],"who_is_affected":"Teams that self-host Heym on a shared backend host where any authenticated user, including the lowest role, can reach the MCP fetch-tools endpoint. Instances that restrict this endpoint to trusted users or do not run Heym before 0.0.75 are less exposed; the sources do not say more.","user_interaction":"no","product_ecosystem":"","needs_special_setup":"no","severity_if_unknown":"high"},"cost_usd":0.000736,"input_tokens":4750,"output_tokens":522,"severity_before":"high"},"analyst_status":null,"analyst_note":null,"search":"'-2026':14A,17A '-67546':15A,18A '/api/mcp/fetch-tools':97C '0.0.75':93C,192C '2':164C 'accept':34B,105C 'advisori':163C 'agent':78C 'ai':20B 'ai-tool':19B 'also':104C 'arg':120C 'argument':49B 'attack':42B,47B,113C,118C 'attacker-suppli':41B,46B,112C,117C 'authent':57B,100C 'autom':84C 'backend':54B,133C 'boundari':180C 'build':75C 'busi':82C 'business-process':81C 'class':156C 'code':65B 'command':9A,44B,115C,148C 'control':184C 'cve':13A,16A 'differ':172C 'distinct':154C 'effect':142C 'egress':183C 'endpoint':33B,98C,168C 'environ':51B,123C 'execut':64B,129C 'exploit':158C 'fail':73B,139C 'fetch':31B 'fetch-tool':30B 'fire':143C 'fix':173C 'gate':175C 'heym':1A,22B,27B,74C 'host':26B,55B,88C,134C 'includ':59B 'infrastructur':89C 'issu':186C 'log':4A 'logged-in':3A 'lowest':61B,102C 'mcp':23B,29B,71B,136C,150C 'merg':124C 'need':170C 'opt':177C 'opt-in':176C 'os.environ':126C 'patch':189C 'post':96C 'primit':159C 'prior':90C 'process':83C,128C 'protocol':137C 'rather':181C 'regardless':144C 'role':62B,103C,174C 'run':8A,77C 'self':25B,87C 'self-host':24B,86C 'server':12A,69B 'share':68B,132C 'side':141C 'spawn':39B,110C 'speak':149C 'ssrf':162C 'stdio':36B,107C 'suppli':43B,48B,114C,119C 'system':79C 'tool':21B,32B 'transport':37B,108C 'trust':179C 'user':6A,58B,101C 'valid':72B,138C 'version':92C,191C 'weak':155C 'whether':146C","nicknames":[],"mitigations":[],"who_affected":"Teams that self-host Heym on a shared backend host where any authenticated user, including the lowest role, can reach the MCP fetch-tools endpoint. Instances that restrict this endpoint to trusted users or do not run Heym before 0.0.75 are less exposed; the sources do not say more.","tier":"B","verified":{},"analyst_revisit_at":null,"fix_status":"available","audience":"businesses","plain_action":null,"pkeys":[],"ptokens":[],"labels":["aitooling","heym","high","mcp","selfhosted"],"campaign_type":null,"search_a":"'-2026':14A,17A '-67546':15A,18A 'command':9A 'cve':13A,16A 'heym':1A 'log':4A 'logged-in':3A 'run':8A 'server':12A 'user':6A","search_b":"'accept':34B 'ai':20B 'ai-tool':19B 'argument':49B 'attack':42B,47B 'attacker-suppli':41B,46B 'authent':57B 'backend':54B 'code':65B 'command':44B 'endpoint':33B 'environ':51B 'execut':64B 'fail':73B 'fetch':31B 'fetch-tool':30B 'heym':22B,27B 'host':26B,55B 'includ':59B 'lowest':61B 'mcp':23B,29B,71B 'role':62B 'self':25B 'self-host':24B 'server':69B 'share':68B 'spawn':39B 'stdio':36B 'suppli':43B,48B 'tool':21B,32B 'transport':37B 'user':58B 'valid':72B","search_c":"'/api/mcp/fetch-tools':97C '0.0.75':93C,192C '2':164C 'accept':105C 'advisori':163C 'agent':78C 'also':104C 'arg':120C 'attack':113C,118C 'attacker-suppli':112C,117C 'authent':100C 'autom':84C 'backend':133C 'boundari':180C 'build':75C 'busi':82C 'business-process':81C 'class':156C 'command':115C,148C 'control':184C 'differ':172C 'distinct':154C 'effect':142C 'egress':183C 'endpoint':98C,168C 'environ':123C 'execut':129C 'exploit':158C 'fail':139C 'fire':143C 'fix':173C 'gate':175C 'heym':74C 'host':88C,134C 'infrastructur':89C 'issu':186C 'lowest':102C 'mcp':136C,150C 'merg':124C 'need':170C 'opt':177C 'opt-in':176C 'os.environ':126C 'patch':189C 'post':96C 'primit':159C 'prior':90C 'process':83C,128C 'protocol':137C 'rather':181C 'regardless':144C 'role':103C,174C 'run':77C 'self':87C 'self-host':86C 'share':132C 'side':141C 'spawn':110C 'speak':149C 'ssrf':162C 'stdio':107C 'suppli':114C,119C 'system':79C 'transport':108C 'trust':179C 'user':101C 'valid':138C 'version':92C,191C 'weak':155C 'whether':146C","cause_entry":null,"cause_path":null,"disclosures_checked_at":null,"first_public_at":"2026-07-21T20:00:25+00:00","kev":null,"cvss_vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","cvss_by":"security-advisories@github.com","poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-67546","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-67546","severity":null,"published_at":"2026-11-11T22:17:29+00:00","modified_at":"2026-11-11T22:17:29+00:00","first_seen_at":"2026-11-11T22:29:35+00:00","fetched_at":"2026-11-11T22:29:35+00:00","note":null}],"documents":[{"id":129454,"url":"https://github.com/heymrun/heym/commit/22b8ee60eb92128cf4ff04a9b6c0e1b62bf25a01","title":"Patch: github.com","kind":"other","source":"nvd","publisher":"vendor","text":null,"published_at":null,"relation":"fix","confidence":null,"note":"Patch: github.com"},{"id":129455,"url":"https://github.com/heymrun/heym/commit/6c6213f88dfa8b2a70d23a9a271171241e910904","title":"Patch: github.com","kind":"other","source":"nvd","publisher":"vendor","text":null,"published_at":null,"relation":"fix","confidence":null,"note":"Patch: github.com"},{"id":129456,"url":"https://github.com/heymrun/heym/releases/tag/v0.0.75","title":"Release notes: github.com","kind":"release","source":"nvd","publisher":"vendor","text":null,"published_at":null,"relation":"fix","confidence":null,"note":"Release notes: github.com"},{"id":129457,"url":"https://github.com/heymrun/heym/security/advisories/GHSA-378x-q589-34mv","title":"Vendor advisory: github.com","kind":"vendor","source":"nvd","publisher":"vendor","text":null,"published_at":"2026-07-21T20:00:25+00:00","relation":"advisory","confidence":null,"note":"Vendor advisory: github.com"}],"disclosures":[],"exploit_sources":[],"notice":"Free to read, with fair use of about 60 pages a minute. For higher limits or API access: sales@infrastack.ai"}