{"id":"CVE-2026-121374","kind":"vulnerability","aliases":["CVE-2026-121374"],"related":[],"title":"Checkmk: Kubernetes agent argument injection lets rule editors run code","description":"Argument injection in the Kubernetes special agent in Checkmk <2.5.0p19, <2.4.0p40, and 2.3.0 (EOL) allows a user with permission to edit rules in at least one folder to write files to arbitrary locations writable by the site user via crafted node roles in the \"Exclude nodes based on their role\" rule option, leading to code execution as the site user.","summary":"The Kubernetes special agent in Checkmk builds command arguments from node roles in the \"Exclude nodes based on their role\" rule option without sanitizing them. A user who can edit rules in at least one folder can write files to any location the site user can write to, which leads to code execution as the site user.","severity":"critical","cvss":9.4,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["checkmk","infrastructure","kubernetes","self-hosted"],"not_affected_if":["auth-required","no-kubernetes-agent"],"how_to_check":"- Check the installed Checkmk version against the affected ranges (`2.5.0p19`, `2.4.0p40`, and 2.3.0 which is end of life).\n- Review who has permission to edit rules in Checkmk folders and whether the Kubernetes special agent is in use.","fix":"- Upgrade Checkmk 2.5.x to `2.5.0p19` or later.\n- Upgrade Checkmk 2.4.x to `2.4.0p40` or later.\n- Checkmk 2.3.0 is end of life; the sources state no fixed version for it.","status":"open","published_at":"2026-11-11T11:17:14+00:00","first_seen_at":"2026-11-11T11:26:55+00:00","triaged_at":"2026-11-11T11:27:27+00:00","updated_at":"2026-11-11T11:27:27+00:00","category":"infrastructure","confidence":0.7,"triage":{"at":"2026-11-11T11:27:27Z","model":"claude-haiku-5-5","output":{"fix":"- Upgrade Checkmk 2.5.x to `2.5.0p19` or later.\n- Upgrade Checkmk 2.4.x to `2.4.0p40` or later.\n- Checkmk 2.3.0 is end of life; the sources state no fixed version for it.","reach":"network","title":"Checkmk: Kubernetes agent argument injection lets rule editors run code","impact":"high","summary":"The Kubernetes special agent in Checkmk builds command arguments from node roles in the \"Exclude nodes based on their role\" rule option without sanitizing them. A user who can edit rules in at least one folder can write files to any location the site user can write to, which leads to code execution as the site user.","audience":"businesses","category":"infrastructure","nicknames":[],"who_cares":["checkmk","kubernetes","self-hosted"],"confidence":0.7,"fix_status":"available","needs_auth":"yes","worst_case":"Code runs as the Checkmk site user on the monitoring server","analyst_note":"","how_to_check":"- Check the installed Checkmk version against the affected ranges (`2.5.0p19`, `2.4.0p40`, and 2.3.0 which is end of life).\n- Review who has permission to edit rules in Checkmk folders and whether the Kubernetes special agent is in use.","plain_action":"","product_name":"","needs_analyst":false,"not_affected_if":["no-kubernetes-agent","auth-required"],"who_is_affected":"Only installations that run the Kubernetes special agent and let users edit rules are exposed. An attacker needs an account with rule-editing permission in at least one folder. Installations without the Kubernetes agent or without such users are less exposed.","user_interaction":"no","product_ecosystem":"","needs_special_setup":"yes","severity_if_unknown":"critical"},"cost_usd":0.000776,"input_tokens":4599,"output_tokens":632,"severity_before":"critical"},"analyst_status":null,"analyst_note":null,"search":"'-121374':13A,16A '-2026':12A,15A '2.3.0':94C '2.4.0':91C '2.5.0':89C 'agent':3A,26B,86C 'allow':96C 'arbitrari':113C 'argument':4A,31B,80C 'base':39B,128C 'build':29B 'checkmk':1A,17B,28B,88C 'code':10A,74B,136C 'command':30B 'craft':121C 'cve':11A,14A 'edit':52B,102C 'editor':8A 'eol':95C 'exclud':37B,126C 'execut':75B,137C 'file':61B,111C 'folder':58B,108C 'host':22B 'infrastructur':18B 'inject':5A,81C 'kubernet':2A,19B,24B,84C 'lead':72B,134C 'least':56B,106C 'let':6A 'locat':64B,114C 'node':33B,38B,122C,127C 'one':57B,107C 'option':44B,133C 'p19':90C 'p40':92C 'permiss':100C 'role':34B,42B,123C,131C 'rule':7A,43B,53B,103C,132C 'run':9A 'sanit':46B 'self':21B 'self-host':20B 'site':66B,78B,118C,140C 'special':25B,85C 'user':49B,67B,79B,98C,119C,141C 'via':120C 'without':45B 'writabl':115C 'write':60B,69B,110C","nicknames":[],"mitigations":[],"who_affected":"Only installations that run the Kubernetes special agent and let users edit rules are exposed. An attacker needs an account with rule-editing permission in at least one folder. Installations without the Kubernetes agent or without such users are less exposed.","tier":"B","verified":{},"analyst_revisit_at":null,"fix_status":"available","audience":"businesses","plain_action":null,"pkeys":[],"ptokens":[],"labels":["checkmk","critical","infrastructure","kubernetes","selfhosted"],"campaign_type":null,"search_a":"'-121374':13A,16A '-2026':12A,15A 'agent':3A 'argument':4A 'checkmk':1A 'code':10A 'cve':11A,14A 'editor':8A 'inject':5A 'kubernet':2A 'let':6A 'rule':7A 'run':9A","search_b":"'agent':26B 'argument':31B 'base':39B 'build':29B 'checkmk':17B,28B 'code':74B 'command':30B 'edit':52B 'exclud':37B 'execut':75B 'file':61B 'folder':58B 'host':22B 'infrastructur':18B 'kubernet':19B,24B 'lead':72B 'least':56B 'locat':64B 'node':33B,38B 'one':57B 'option':44B 'role':34B,42B 'rule':43B,53B 'sanit':46B 'self':21B 'self-host':20B 'site':66B,78B 'special':25B 'user':49B,67B,79B 'without':45B 'write':60B,69B","search_c":"'2.3.0':94C '2.4.0':91C '2.5.0':89C 'agent':86C 'allow':96C 'arbitrari':113C 'argument':80C 'base':128C 'checkmk':88C 'code':136C 'craft':121C 'edit':102C 'eol':95C 'exclud':126C 'execut':137C 'file':111C 'folder':108C 'inject':81C 'kubernet':84C 'lead':134C 'least':106C 'locat':114C 'node':122C,127C 'one':107C 'option':133C 'p19':90C 'p40':92C 'permiss':100C 'role':123C,131C 'rule':103C,132C 'site':118C,140C 'special':85C 'user':98C,119C,141C 'via':120C 'writabl':115C 'write':110C","cause_entry":null,"cause_path":null,"disclosures_checked_at":null,"first_public_at":"2026-11-11T11:17:14+00:00","kev":null,"cvss_vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/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":"security@checkmk.com","poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-121374","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-121374","severity":null,"published_at":"2026-11-11T11:17:14+00:00","modified_at":"2026-11-11T11:17:14+00:00","first_seen_at":"2026-11-11T11:26:55+00:00","fetched_at":"2026-11-11T11:26:55+00:00","note":null}],"documents":[],"disclosures":[],"exploit_sources":[],"notice":"Free to read, with fair use of about 60 pages a minute. 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