{"id":"CVE-2025-3935","published":"2025-04-25T19:15:49Z","modified":"2026-06-17T09:20:57Z","title":"ConnectWise ScreenConnect Improper Authentication Vulnerability","vendor":"ConnectWise","product":"ScreenConnect","tier":"core","eol":null,"description":{"text":"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.","provenance":"source","from":"NVD"},"summary":{"text":"ConnectWise ScreenConnect (versions 25.2.3 and earlier) is susceptible to ViewState code injection, a platform-level weakness in how ASP.NET Web Forms preserve state, rather than a flaw introduced by ScreenConnect itself. An attacker who has already obtained the platform's machine keys, which requires privileged system-level access, could send a crafted malicious ViewState to the website and potentially achieve remote code execution on the server.","provenance":"ai","model":"claude-haiku-5-5","generatedAt":"2026-10-23T07:14:16Z"},"cvss":{"score":7.2,"severity":"HIGH","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H","provenance":"source","from":"NVD"},"epss":{"score":0.03597,"percentile":0.89423,"date":"2026-10-29","provenance":"source"},"kev":{"dateAdded":"2025-06-02","dueDate":"2025-06-23","ransomware":false,"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.","notes":"https://www.connectwise.com/company/trust/security-bulletins/screenconnect-security-patch-2025.4 ;   https://nvd.nist.gov/vuln/detail/CVE-2025-3935","provenance":"source"},"vulncheckKev":{"dateAdded":"2025-05-30","exploitedFirstSeen":"2025-05-30","ransomware":false,"evidence":[{"url":"https://thehackernews.com/2025/05/connectwise-hit-by-cyberattack-nation.html","date":"2025-05-30"},{"url":"https://www.cisa.gov/sites/default/files/feeds/known_exploited_vulnerabilities.json","date":"2025-06-02"},{"url":"https://falconfeeds.io/blogs/unmasking-handala-iran-cyber-threat-psyops","date":"2025-06-16"},{"url":"https://www.withsecure.com/content/dam/with-secure/en/resources/THR_May25.pdf","date":"2025-06-25"},{"url":"https://hunt.io/blog/asyncrat-screenconnect-open-directory-campaigns","date":"2025-09-18"},{"url":"https://www.loginsoft.com/reports/annually/vulnerability-intelligence-report-2025","date":"2026-01-20"}],"evidenceTotal":6,"provenance":"source"},"exploited":true,"otx":{"pulseCount":50,"pulses":[{"name":"Actively_Exploited_Kev | Oct 30, 2026","url":"https://otx.alienvault.com/pulse/6ae35d889ea92b4ce19c2680","created":"2026-10-29"},{"name":"Actively_Exploited_Kev | Oct 29, 2026","url":"https://otx.alienvault.com/pulse/6ae20c1db17e7057ae7d9ad1","created":"2026-10-28"},{"name":"Actively_Exploited_Kev | Oct 28, 2026","url":"https://otx.alienvault.com/pulse/6ae0ba7e0e2a97ff7b218819","created":"2026-10-27"},{"name":"Actively_Exploited_Kev | Oct 27, 2026","url":"https://otx.alienvault.com/pulse/6adf68b85c3e852f3c111d18","created":"2026-10-26"},{"name":"Actively_Exploited_Kev | Oct 24, 2026","url":"https://otx.alienvault.com/pulse/6adb740e397c3ad4799aa4cd","created":"2026-10-23"},{"name":"Actively_Exploited_Kev | Oct 23, 2026","url":"https://otx.alienvault.com/pulse/6ada236fcfba2dfa730ea482","created":"2026-10-22"},{"name":"Actively_Exploited_Kev | Oct 22, 2026","url":"https://otx.alienvault.com/pulse/6ad8d33a077cbb5cab524d80","created":"2026-10-21"},{"name":"Actively_Exploited_Kev | Oct 21, 2026","url":"https://otx.alienvault.com/pulse/6ad78130c4d1ac2be83a8b6d","created":"2026-10-20"},{"name":"Actively_Exploited_Kev | Oct 20, 2026","url":"https://otx.alienvault.com/pulse/6ad62f63c24a405a3423cc13","created":"2026-10-19"},{"name":"Actively_Exploited_Kev | Oct 19, 2026","url":"https://otx.alienvault.com/pulse/6ad4dda174e5797d0bd238b7","created":"2026-10-18"}],"provenance":"machine"},"cwes":[{"id":"CWE-502","name":"Deserialization of Untrusted Data"},{"id":"CWE-287","name":"Improper Authentication"}],"references":[{"url":"https://www.connectwise.com/company/trust/advisories","tags":["Vendor Advisory"]},{"url":"https://www.connectwise.com/company/trust/security-bulletins/screenconnect-security-patch-2025.4","tags":["Vendor Advisory"]},{"url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-3935","tags":["US Government Resource"]}],"techniques":[{"id":"T1203","name":"Exploitation for Client Execution","tactics":["execution"],"provenance":"source","basis":"ctid-kev","bases":["ctid-kev"],"basisDetail":"CTID Mappings Explorer KEV 07/28/2025 (ATT&CK 16.1); capability: Improper Access Control","mappingType":"exploitation_technique","evidence":[],"comment":"By exploiting this vulnerability, which stems from ASP.NET and its use of ViewState, an attacker with privileged access can gain access to sensitive data, such as machine keys. By using these machine keys, the attacker can craft malicious ViewState payloads to execute remote code on the ScreenConnect server.","confidence":"low","confidenceNote":"server-side bug exploitable without user interaction; client-execution technique does not fit"},{"id":"T1059","name":"Command and Scripting Interpreter","tactics":["execution"],"provenance":"source","basis":"ctid-kev","bases":["ctid-kev"],"basisDetail":"CTID Mappings Explorer KEV 07/28/2025 (ATT&CK 16.1); capability: Improper Access Control","mappingType":"primary_impact","evidence":[],"comment":"By exploiting this vulnerability, which stems from ASP.NET and its use of ViewState, an attacker with privileged access can gain access to sensitive data, such as machine keys. By using these machine keys, the attacker can craft malicious ViewState payloads to execute remote code on the ScreenConnect server.","confidence":"high"}],"reports":[],"affected":[],"advisories":[],"euvd":{"id":"EUVD-2025-12502","url":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2025-12502","exploited":true,"exploitedSince":"2025-06-02","provenance":"source"},"exploits":[],"exploitSources":null,"exploitRefs":[],"flow":[{"stage":"primary","techniques":["T1059"],"provenance":"source"},{"stage":"related","techniques":["T1203"],"provenance":"source","lowConfidence":true}],"timeline":[{"date":"2025-04-25","kind":"published","label":"Published (NVD)","url":"https://nvd.nist.gov/vuln/detail/CVE-2025-3935","provenance":"source"},{"date":"2025-05-30","kind":"exploited-reported","label":"Exploitation first reported (VulnCheck KEV evidence)","url":"https://thehackernews.com/2025/05/connectwise-hit-by-cyberattack-nation.html","provenance":"source"},{"date":"2025-06-02","kind":"kev","label":"Added to CISA KEV","url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","provenance":"source"},{"date":"2025-06-02","kind":"euvd-exploited","label":"ENISA EUVD: exploited","url":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2025-12502","provenance":"source"}],"speed":{"daysToPublicExploit":null,"firstExploitFrom":null,"daysToKev":38},"priority":{"score":60.9,"factors":[{"name":"In a KEV catalog","points":35.0,"detail":"listed in CISA KEV and VulnCheck KEV"},{"name":"Recent KEV listing","points":0.0,"detail":"added 518 days ago"},{"name":"Known ransomware use","points":0.0,"detail":"not known"},{"name":"EPSS percentile","points":17.88,"detail":"percentile 0.8942"},{"name":"Named in threat reports","points":0.0,"detail":"0 reports"},{"name":"Public exploit code","points":0.0,"detail":"none found"},{"name":"Mentioned in OTX pulses","points":3.0,"detail":"50 pulses"},{"name":"CVSS severity","points":5.04,"detail":"base score 7.2"},{"name":"End-of-life product","points":0.0,"detail":"supported or unknown"}]}}