{"id":"CVE-2026-123838","kind":"vulnerability","aliases":["CVE-2026-123838"],"related":[],"title":"JetBrains IntelliJ IDEA: opening a UI Designer form runs code in Safe Mode","description":"In JetBrains IntelliJ IDEA before 2026.3 code execution was possible in Safe Mode via UI Designer form file","summary":"In JetBrains IntelliJ IDEA before 2026.3, a crafted UI Designer form file could make the IDE execute code even while it was in Safe Mode. An attacker who gets a developer to open such a file in the IDE can run code as that developer.","severity":"high","cvss":7.8,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["intellij-idea","java","jetbrains","kotlin","runtime"],"not_affected_if":["only-trusted-projects","version-2026.3-or-later"],"how_to_check":"- Check the installed IntelliJ IDEA version under Help > About; versions before `2026.3` are in scope.","fix":"- JetBrains IntelliJ IDEA: move to `2026.3` or later (per the sources' description: fixed in `2026.3`).","status":"open","published_at":"2026-11-06T17:17:22+00:00","first_seen_at":"2026-11-06T17:43:12+00:00","triaged_at":"2026-11-06T17:45:00+00:00","updated_at":"2026-11-06T17:45:00+00:00","category":"runtime","confidence":0.6,"triage":{"at":"2026-11-06T17:45:00Z","model":"claude-haiku-5-5","output":{"fix":"- JetBrains IntelliJ IDEA: move to `2026.3` or later (per the sources' description: fixed in `2026.3`).","reach":"local","title":"JetBrains IntelliJ IDEA: opening a UI Designer form runs code in Safe Mode","impact":"high","summary":"In JetBrains IntelliJ IDEA before 2026.3, a crafted UI Designer form file could make the IDE execute code even while it was in Safe Mode. An attacker who gets a developer to open such a file in the IDE can run code as that developer.","audience":"developers","category":"runtime","nicknames":[],"who_cares":["intellij-idea","jetbrains","java","kotlin"],"confidence":0.6,"fix_status":"available","needs_auth":"no","worst_case":"code runs on the developer's machine with their privileges","analyst_note":"Confirm from the JetBrains advisory whether opening the file is the only trigger and whether Safe Mode is the only protection bypassed; the NVD entry gives only the description.","how_to_check":"- Check the installed IntelliJ IDEA version under Help > About; versions before `2026.3` are in scope.\n- Unknown whether the sources name any other check.","plain_action":"","needs_analyst":true,"not_affected_if":["version-2026.3-or-later","only-trusted-projects"],"who_is_affected":"Developers who open projects or files from untrusted sources in IntelliJ IDEA versions before 2026.3. The sources do not describe other configurations; Safe Mode was expected to block this and did not.","user_interaction":"yes","needs_special_setup":"unknown","severity_if_unknown":"high"},"cost_usd":0.000705,"input_tokens":4175,"output_tokens":574,"severity_before":"high"},"analyst_status":null,"analyst_note":null,"search":"'-123838':16A,19A '-2026':15A,18A '2026.3':32B,77C 'attack':53B 'code':10A,44B,68B,78C 'could':39B 'craft':34B 'cve':14A,17A 'design':7A,36B,87C 'develop':57B,71B 'even':45B 'execut':43B,79C 'file':38B,62B,89C 'form':8A,37B,88C 'get':55B 'ide':42B,65B 'idea':3A,22B,30B,75C 'intellij':2A,21B,29B,74C 'intellij-idea':20B 'java':23B 'jetbrain':1A,24B,28B,73C 'kotlin':25B 'make':40B 'mode':13A,51B,84C 'open':4A,59B 'possibl':81C 'run':9A,67B 'runtim':26B 'safe':12A,50B,83C 'ui':6A,35B,86C 'via':85C","nicknames":[],"mitigations":[],"who_affected":"Developers who open projects or files from untrusted sources in IntelliJ IDEA versions before 2026.3. The sources do not describe other configurations; Safe Mode was expected to block this and did not.","tier":"B","verified":{},"analyst_revisit_at":null,"fix_status":"available","audience":"developers","plain_action":null,"pkeys":[],"ptokens":[],"labels":["high","intellijidea","java","jetbrains","kotlin","runtime"],"campaign_type":null,"search_a":"'-123838':16A,19A '-2026':15A,18A 'code':10A 'cve':14A,17A 'design':7A 'form':8A 'idea':3A 'intellij':2A 'jetbrain':1A 'mode':13A 'open':4A 'run':9A 'safe':12A 'ui':6A","search_b":"'2026.3':32B 'attack':53B 'code':44B,68B 'could':39B 'craft':34B 'design':36B 'develop':57B,71B 'even':45B 'execut':43B 'file':38B,62B 'form':37B 'get':55B 'ide':42B,65B 'idea':22B,30B 'intellij':21B,29B 'intellij-idea':20B 'java':23B 'jetbrain':24B,28B 'kotlin':25B 'make':40B 'mode':51B 'open':59B 'run':67B 'runtim':26B 'safe':50B 'ui':35B","search_c":"'2026.3':77C 'code':78C 'design':87C 'execut':79C 'file':89C 'form':88C 'idea':75C 'intellij':74C 'jetbrain':73C 'mode':84C 'possibl':81C 'safe':83C 'ui':86C 'via':85C","first_public_at":"2026-11-06T17:17:22+00:00","kev":null,"cvss_vector":"CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H","cvss_by":"cve@jetbrains.com","poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-123838","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-123838","severity":null,"published_at":"2026-11-06T17:17:22+00:00","modified_at":"2026-11-06T17:17:22+00:00","first_seen_at":"2026-11-06T17:43:12+00:00","fetched_at":"2026-11-06T17:43:12+00:00","note":null}],"documents":[],"exploit_sources":[],"notice":"Free to read, with fair use of about 60 pages a minute. For higher limits or API access: sales@infrastack.ai"}