{"id":"CVE-2026-123854","kind":"vulnerability","aliases":["CVE-2026-123854"],"related":[],"title":"JetBrains PyCharm: crafted Jupyter notebook runs code even in Safe Mode","description":"In JetBrains PyCharm before 2026.3 code execution was possible in Safe Mode via a crafted Jupyter notebook widget module","summary":"Before PyCharm 2026.3, a crafted Jupyter notebook widget module could execute code while PyCharm was in Safe Mode. An attacker who gets a developer to open such a notebook can run code on that developer's machine.","severity":"medium","cvss":5.5,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["jupyter","other","pycharm","python"],"not_affected_if":["pycharm-2026.3-or-later"],"how_to_check":"- Check the installed PyCharm version under Help > About\n- Compare it with `2026.3`; anything earlier is in the affected range","fix":"- JetBrains PyCharm: upgrade to `2026.3` or later","status":"open","published_at":"2026-11-06T17:17:24+00:00","first_seen_at":"2026-11-06T17:43:13+00:00","triaged_at":"2026-11-06T17:45:21+00:00","updated_at":"2026-11-06T17:45:21+00:00","category":"other","confidence":0.6,"triage":{"at":"2026-11-06T17:45:21Z","model":"claude-haiku-5-5","output":{"fix":"- JetBrains PyCharm: upgrade to `2026.3` or later","reach":"local","title":"JetBrains PyCharm: crafted Jupyter notebook runs code even in Safe Mode","impact":"high","summary":"Before PyCharm 2026.3, a crafted Jupyter notebook widget module could execute code while PyCharm was in Safe Mode. An attacker who gets a developer to open such a notebook can run code on that developer's machine.","audience":"developers","category":"other","nicknames":[],"who_cares":["pycharm","jupyter","python"],"confidence":0.6,"fix_status":"available","needs_auth":"no","worst_case":"code runs on the developer's machine via a notebook","analyst_note":"","how_to_check":"- Check the installed PyCharm version under Help > About\n- Compare it with `2026.3`; anything earlier is in the affected range","plain_action":"","needs_analyst":false,"not_affected_if":["pycharm-2026.3-or-later"],"who_is_affected":"Developers who open Jupyter notebooks in PyCharm versions before 2026.3, including notebooks from untrusted sources. The sources do not say whether the flaw needs a particular notebook feature enabled beyond opening the file. Teams that only use PyCharm on trusted notebooks face lower risk but should still upgrade.","user_interaction":"yes","needs_special_setup":"unknown","severity_if_unknown":"medium"},"cost_usd":0.00067,"input_tokens":4182,"output_tokens":503,"severity_before":"medium"},"analyst_status":null,"analyst_note":null,"search":"'-123854':14A,17A '-2026':13A,16A '2026.3':24B,63C 'attack':41B 'code':7A,33B,53B,64C 'could':31B 'craft':3A,26B,73C 'cve':12A,15A 'develop':45B,56B 'even':8A 'execut':32B,65C 'get':43B 'jetbrain':1A,60C 'jupyt':4A,18B,27B,74C 'machin':58B 'mode':11A,39B,70C 'modul':30B,77C 'notebook':5A,28B,50B,75C 'open':47B 'possibl':67C 'pycharm':2A,20B,23B,35B,61C 'python':21B 'run':6A,52B 'safe':10A,38B,69C 'via':71C 'widget':29B,76C","nicknames":[],"mitigations":[],"who_affected":"Developers who open Jupyter notebooks in PyCharm versions before 2026.3, including notebooks from untrusted sources. The sources do not say whether the flaw needs a particular notebook feature enabled beyond opening the file. Teams that only use PyCharm on trusted notebooks face lower risk but should still upgrade.","tier":"C","verified":{},"analyst_revisit_at":null,"fix_status":"available","audience":"developers","plain_action":null,"pkeys":[],"ptokens":[],"labels":["jupyter","medium","other","pycharm","python"],"campaign_type":null,"search_a":"'-123854':14A,17A '-2026':13A,16A 'code':7A 'craft':3A 'cve':12A,15A 'even':8A 'jetbrain':1A 'jupyt':4A 'mode':11A 'notebook':5A 'pycharm':2A 'run':6A 'safe':10A","search_b":"'2026.3':24B 'attack':41B 'code':33B,53B 'could':31B 'craft':26B 'develop':45B,56B 'execut':32B 'get':43B 'jupyt':18B,27B 'machin':58B 'mode':39B 'modul':30B 'notebook':28B,50B 'open':47B 'pycharm':20B,23B,35B 'python':21B 'run':52B 'safe':38B 'widget':29B","search_c":"'2026.3':63C 'code':64C 'craft':73C 'execut':65C 'jetbrain':60C 'jupyt':74C 'mode':70C 'modul':77C 'notebook':75C 'possibl':67C 'pycharm':61C 'safe':69C 'via':71C 'widget':76C","first_public_at":"2026-11-06T17:17:24+00:00","kev":null,"cvss_vector":"CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N","cvss_by":"cve@jetbrains.com","poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-123854","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-123854","severity":null,"published_at":"2026-11-06T17:17:24+00:00","modified_at":"2026-11-06T17:17:24+00:00","first_seen_at":"2026-11-06T17:43:13+00:00","fetched_at":"2026-11-06T17:43:13+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"}