{"id":"CVE-2026-118678","kind":"vulnerability","aliases":["CVE-2026-118678"],"related":[],"title":"n8n: prototype pollution via workflow connection keys breaks logins and writes","description":"n8n before 2.41.4 and 2.42.x before 2.42.1 contains a prototype pollution vulnerability that allows low-privileged users to alter built-in object behaviour by saving workflows with specially named connection keys. Attackers can add keys such as __proto__ to workflow connections, which the periodic history compaction task processes, causing logins and writes to fail with server errors.","summary":"n8n before 2.41.4 and 2.42.x before 2.42.1 lets a low-privileged user save a workflow with keys such as __proto__ in its connections. The periodic history compaction task processes those keys and alters built-in object behaviour, so logins and writes fail with server errors.","severity":"high","cvss":7.1,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["ai-tooling","n8n","self-hosted","workflow-automation"],"not_affected_if":["admin-only-workflow-editing","managed-hosting"],"how_to_check":"- Run `n8n --version` (or check the image tag) and compare against `2.41.4` and `2.42.1`\n- Look for workflows whose connections object contains a `__proto__` key\n- unknown","fix":"- Upgrade n8n to `2.41.4` on the 2.41 line, or to `2.42.1` on the 2.42 line\n- unknown","status":"open","published_at":"2026-10-28T19:17:33+00:00","first_seen_at":"2026-10-28T19:34:55+00:00","triaged_at":"2026-10-28T19:36:04+00:00","updated_at":"2026-10-28T19:36:04+00:00","category":"ai-tooling","confidence":0.6,"triage":{"at":"2026-10-28T19:36:04Z","model":"claude-haiku-5-5","output":{"fix":"- Upgrade n8n to `2.41.4` on the 2.41 line, or to `2.42.1` on the 2.42 line\n- unknown","reach":"network","title":"n8n: prototype pollution via workflow connection keys breaks logins and writes","impact":"medium","summary":"n8n before 2.41.4 and 2.42.x before 2.42.1 lets a low-privileged user save a workflow with keys such as __proto__ in its connections. The periodic history compaction task processes those keys and alters built-in object behaviour, so logins and writes fail with server errors.","category":"ai-tooling","nicknames":[],"who_cares":["n8n","self-hosted","workflow-automation"],"confidence":0.6,"needs_auth":"yes","worst_case":"Logins and workflow writes fail with server errors until repaired","analyst_note":"Check the n8n GitHub advisory for the fix commit and whether the impact extends beyond denial of service on logins and writes.","how_to_check":"- Run `n8n --version` (or check the image tag) and compare against `2.41.4` and `2.42.1`\n- Look for workflows whose connections object contains a `__proto__` key\n- unknown","needs_analyst":true,"not_affected_if":["managed-hosting","admin-only-workflow-editing"],"who_is_affected":"Self-hosted n8n instances that let low-privileged users create or save workflows are exposed, because those users can plant the malicious connection keys. Instances where only trusted administrators can edit workflows face less risk. Managed n8n hosting is handled by the vendor. Sources do not say whether the impact is limited to the server-error denial of service described or extends beyond it.","user_interaction":"no","needs_special_setup":"unknown","severity_if_unknown":"high"},"cost_usd":0.000641,"input_tokens":3353,"output_tokens":611,"severity_before":"high"},"analyst_status":null,"analyst_note":null,"search":"'-118678':14A,17A '-2026':13A,16A '2.41.4':30B,78C '2.42':32B,80C '2.42.1':35B,83C 'add':112C 'ai':19B 'ai-tool':18B 'allow':90C 'alter':62B,96C 'attack':110C 'autom':27B 'behaviour':67B,101C 'break':8A 'built':64B,98C 'built-in':63B,97C 'caus':127C 'compact':56B,124C 'connect':6A,52B,108C,119C 'contain':84C 'cve':12A,15A 'error':75B,135C 'fail':72B,132C 'histori':55B,123C 'host':24B 'key':7A,46B,60B,109C,113C 'let':36B 'login':9A,69B,128C 'low':39B,92C 'low-privileg':38B,91C 'n8n':1A,21B,28B,76C 'name':107C 'object':66B,100C 'period':54B,122C 'pollut':3A,87C 'privileg':40B,93C 'process':58B,126C 'proto':49B,116C 'prototyp':2A,86C 'save':42B,103C 'self':23B 'self-host':22B 'server':74B,134C 'special':106C 'task':57B,125C 'tool':20B 'user':41B,94C 'via':4A 'vulner':88C 'workflow':5A,26B,44B,104C,118C 'workflow-autom':25B 'write':11A,71B,130C 'x':33B,81C","nicknames":[],"mitigations":[],"who_affected":"Self-hosted n8n instances that let low-privileged users create or save workflows are exposed, because those users can plant the malicious connection keys. Instances where only trusted administrators can edit workflows face less risk. Managed n8n hosting is handled by the vendor. Sources do not say whether the impact is limited to the server-error denial of service described or extends beyond it.","tier":"B","verified":{},"analyst_revisit_at":null,"first_public_at":"2026-10-28T19:17:33+00:00","kev":null,"cvss_vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","cvss_by":"disclosure@vulncheck.com","poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-118678","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-118678","severity":null,"published_at":"2026-10-28T19:17:33+00:00","modified_at":"2026-10-28T19:17:34+00:00","first_seen_at":"2026-10-28T19:34:55+00:00","fetched_at":"2026-10-28T19:34:55+00:00","note":null}],"documents":[],"notice":"Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai"}