{"id":"CVE-2025-3935","kind":"vulnerability","aliases":["CVE-2025-3935"],"related":[],"title":"connectwise screenconnect: ScreenConnect versions 25.2.3 and earlier versions may be susceptible to a ViewState code injection attack","description":"ScreenConnect versions 25.2.3 and earlier versions may be susceptible to a ViewState code injection attack. ASP.NET Web Forms use ViewState to preserve page and control state, with data encoded using Base64 protected by machine keys. \nIt is important to note that to obtain these machine keys, privileged system level access must be obtained. \n\n\n\nIf these machine keys are compromised, attackers could create and send a malicious ViewState to the website, potentially leading to remote code execution on the server. \n\n\n\nThe risk does not originate from a vulnerability introduced by ScreenConnect, but from platform level behavior.  This had no direct impact to ScreenConnect Client. ScreenConnect 2025.4 patch disables ViewState and removes any dependency on it.","summary":"ConnectWise ScreenConnect has an improper authentication flaw that allows ViewState code injection, which can lead to remote code execution if machine keys are compromised. CISA lists it as actively exploited in the wild.","severity":"high","cvss":8.1,"epss":null,"exploited":true,"exploited_at":"2025-06-02T00:00:00+00:00","products":[{"name":"connectwise screenconnect","fixed":["25.2.4"],"affected":"< 25.2.4","ecosystem":"vendor"},{"name":"ConnectWise ScreenConnect","fixed":[],"affected":"","ecosystem":"vendor"}],"ecosystems":["vendor"],"tags":["connectwise","exploited","screenconnect","self-hosted","vendor"],"not_affected_if":["managed-hosting","unknown"],"how_to_check":null,"fix":"Apply mitigations per vendor instructions, or discontinue use of the product if mitigations are unavailable (per CISA required action).","status":"open","published_at":"2025-04-25T19:15:49+00:00","first_seen_at":"2026-10-23T19:11:51+00:00","triaged_at":"2026-10-23T20:48:26+00:00","updated_at":"2026-10-24T00:09:50+00:00","category":"vendor","confidence":0.5,"triage":{"at":"2026-10-23T20:48:26Z","model":"claude-haiku-5-5","output":{"fix":"Apply mitigations per vendor instructions, or discontinue use of the product if mitigations are unavailable (per CISA required action).","reach":"unknown","summary":"ConnectWise ScreenConnect has an improper authentication flaw that allows ViewState code injection, which can lead to remote code execution if machine keys are compromised. CISA lists it as actively exploited in the wild.","category":"vendor","who_cares":["screenconnect","connectwise","self-hosted"],"confidence":0.5,"needs_auth":"unknown","worst_case":"Attacker runs code on the ScreenConnect server if machine keys are compromised","analyst_note":"Sources give no affected or fixed versions and no mitigation steps; check the ConnectWise security advisory for CVE-2025-3935 for versions, fixes and machine key guidance.","how_to_check":"unknown","needs_analyst":true,"not_affected_if":["managed-hosting","unknown"],"user_interaction":"unknown","needs_special_setup":"unknown","severity_if_unknown":"unknown"},"cost_usd":0.00044,"input_tokens":2557,"output_tokens":368,"severity_before":"unknown"},"analyst_status":null,"analyst_note":null,"search":"'-2025':19A,22A '-3935':20A,23A '2025.4':172C '25.2.3':5A,70C 'access':117C 'activ':63B 'allow':43B 'asp.net':83C 'attack':17A,82C,127C 'authent':40B 'base64':98C 'behavior':162C 'cisa':59B 'client':170C 'code':15A,45B,52B,80C,142C 'compromis':58B,126C 'connectwis':1A,28B,35B 'connectwise':24A,26A 'control':92C 'could':128C 'creat':129C 'cve':18A,21A 'data':95C 'depend':179C 'direct':166C 'disabl':174C 'earlier':7A,72C 'encod':96C 'execut':53B,143C 'exploit':29B,64B 'flaw':41B 'form':85C 'host':33B 'impact':167C 'import':105C 'improp':39B 'inject':16A,46B,81C 'introduc':155C 'key':56B,102C,113C,124C 'lead':49B,139C 'level':116C,161C 'list':60B 'machin':55B,101C,112C,123C 'malici':133C 'may':9A,74C 'must':118C 'note':107C 'obtain':110C,120C 'origin':151C 'page':90C 'patch':173C 'platform':160C 'potenti':138C 'preserv':89C 'privileg':114C 'protect':99C 'remot':51B,141C 'remov':177C 'risk':148C 'screenconnect':2A,3A,25A,27A,30B,36B,68C,157C,169C,171C 'self':32B 'self-host':31B 'send':131C 'server':146C 'state':93C 'suscept':11A,76C 'system':115C 'use':86C,97C 'vendor':34B 'version':4A,8A,69C,73C 'viewstat':14A,44B,79C,87C,134C,175C 'vulner':154C 'web':84C 'websit':137C 'wild':67B","nicknames":[],"mitigations":[],"who_affected":null,"tier":null,"verified":{},"analyst_revisit_at":null,"first_public_at":"2025-04-25T19:15:49+00:00","kev":{"dateAdded":"2025-06-02","dueDate":"2025-06-23","requiredAction":"Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.","knownRansomwareCampaignUse":"Unknown"},"cvss_vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H","cvss_by":"7d616e1a-3288-43b1-a0dd-0a65d3e70a49","poc_count":0,"sources":[{"source":"kev","external_id":"CVE-2025-3935","url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2025-3935","severity":null,"published_at":"2025-06-02T00:00:00+00:00","modified_at":null,"first_seen_at":"2026-10-23T19:11:51+00:00","fetched_at":"2026-10-25T12:39:22+00:00","note":null},{"source":"nvd","external_id":"CVE-2025-3935","url":"https://nvd.nist.gov/vuln/detail/CVE-2025-3935","severity":null,"published_at":"2025-04-25T19:15:49+00:00","modified_at":"2026-06-17T09:20:57+00:00","first_seen_at":"2026-10-23T22:29:05+00:00","fetched_at":"2026-10-23T22:29:05+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"}