{"id":"CVE-2026-91484","kind":"vulnerability","aliases":["CVE-2026-91484"],"related":[],"title":"Java SE: plugin flaw lets low-privilege users escape the sandbox","description":"Vulnerability in Oracle Java SE (component: Java plugin).  Supported versions that are affected are Oracle Java SE: 8u503 and  8u503-perf. Difficult to exploit vulnerability allows low privileged attacker with logon to the infrastructure where Oracle Java SE executes to compromise Oracle Java SE.  While the vulnerability is in Oracle Java SE, attacks may significantly impact additional products (scope change).  Successful attacks of this vulnerability can result in  unauthorized creation, deletion or modification access to critical data or all Oracle Java SE accessible data as well as  unauthorized access to critical data or complete access to all Oracle Java SE accessible data. Note: This vulnerability applies to Java deployments, typically in clients running sandboxed Java Web Start applications or sandboxed Java applets, that load and run untrusted code (e.g., code that comes from the internet) and rely on the Java sandbox for security. This vulnerability does not apply to Java deployments, typically in servers, that load and run only trusted code (e.g., code installed by an administrator). CVSS 3.1 Base Score 7.5 (Confidentiality and Integrity impacts).  CVSS Vector: (CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:N).","summary":"The Java plugin in Oracle Java SE 8u503 has a flaw that lets an attacker with low privileges on the machine compromise the runtime. The description says the attack targets sandboxed Java Web Start applications and applets that run untrusted code from the internet.","severity":"high","cvss":7.5,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["desktop-clients","java","oracle-java-se","runtime"],"not_affected_if":["no-applets-or-web-start","server-only-trusted-code"],"how_to_check":"- Run `java -version` and compare against 8u503 (affected) and later builds\n- Check whether Java Web Start or browser applets are enabled on client machines\n- unknown for whether any server-side Java deployment is exposed","fix":"- Upgrade Oracle Java SE 8 past `8u503` to a patched release (unknown exact fixed build)\n- Disable the Java browser plugin and Java Web Start where they are not needed","status":"open","published_at":"2026-10-20T22:20:52+00:00","first_seen_at":"2026-10-23T21:57:27+00:00","triaged_at":"2026-10-25T03:18:21+00:00","updated_at":"2026-10-25T03:18:21+00:00","category":"runtime","confidence":0.6,"triage":{"at":"2026-10-25T03:18:21Z","model":"claude-haiku-5-5","output":{"fix":"- Upgrade Oracle Java SE 8 past `8u503` to a patched release (unknown exact fixed build)\n- Disable the Java browser plugin and Java Web Start where they are not needed","reach":"local","title":"Java SE: plugin flaw lets low-privilege users escape the sandbox","impact":"high","summary":"The Java plugin in Oracle Java SE 8u503 has a flaw that lets an attacker with low privileges on the machine compromise the runtime. The description says the attack targets sandboxed Java Web Start applications and applets that run untrusted code from the internet.","category":"runtime","nicknames":[],"who_cares":["java","oracle-java-se","desktop-clients"],"confidence":0.6,"needs_auth":"yes","worst_case":"attacker reads and modifies data the Java runtime can access","analyst_note":"Confirm fixed Java SE 8 build number and whether user interaction is required, using the Oracle Critical Patch Update advisory for this CVE.","how_to_check":"- Run `java -version` and compare against 8u503 (affected) and later builds\n- Check whether Java Web Start or browser applets are enabled on client machines\n- unknown for whether any server-side Java deployment is exposed","needs_analyst":true,"not_affected_if":["server-only-trusted-code","no-applets-or-web-start"],"who_is_affected":"Affected deployments are Java clients that run sandboxed Web Start applications or applets loading untrusted internet code and relying on the Java sandbox. Server-side Java that runs only administrator-installed trusted code is not affected according to the description.","user_interaction":"unknown","needs_special_setup":"yes","severity_if_unknown":"high"},"cost_usd":0.000661,"input_tokens":3657,"output_tokens":591,"severity_before":"high"},"analyst_status":null,"analyst_note":null,"search":"'-2026':14A,17A '-91484':15A,18A '/av':253C '3.1':241C,252C '7.5':244C '8u503':35B,89C,92C '8u503-perf':91C 'access':146C,155C,161C,167C,173C 'addit':129C 'administr':239C 'affect':84C 'allow':98C 'applet':64B,194C 'appli':178C,220C 'applic':62B,190C 'attack':42B,56B,101C,125C,134C 'base':242C 'c/c':258C 'chang':132C 'client':21B,184C 'code':68B,200C,202C,233C,235C 'come':204C 'complet':166C 'compon':77C 'compromis':49B,113C 'confidenti':245C 'creation':142C 'critic':148C,163C 'cve':13A,16A 'cvss':240C,249C,251C 'data':149C,156C,164C,174C 'delet':143C 'deploy':181C,223C 'descript':53B 'desktop':20B 'desktop-cli':19B 'difficult':94C 'e.g':201C,234C 'escap':10A 'execut':111C 'exploit':96C 'flaw':4A,38B 'h/a':260C 'h/i':259C 'h/pr':255C 'impact':128C,248C 'infrastructur':106C 'instal':236C 'integr':247C 'internet':71B,207C 'java':1A,22B,25B,29B,33B,59B,75C,78C,87C,109C,115C,123C,153C,171C,180C,187C,193C,212C,222C 'l/ac':254C 'l/ui':256C 'let':5A,40B 'load':196C,228C 'logon':103C 'low':7A,44B,99C 'low-privileg':6A 'machin':48B 'may':126C 'modif':145C 'n':261C 'n/s':257C 'note':175C 'oracl':24B,32B,74C,86C,108C,114C,122C,152C,170C 'oracle-java-s':23B 'perf':93C 'plugin':3A,30B,79C 'privileg':8A,45B,100C 'product':130C 'reli':209C 'result':139C 'run':66B,185C,198C,230C 'runtim':27B,51B 'sandbox':12A,58B,186C,192C,213C 'say':54B 'scope':131C 'score':243C 'se':2A,26B,34B,76C,88C,110C,116C,124C,154C,172C 'secur':215C 'server':226C 'signific':127C 'start':61B,189C 'success':133C 'support':80C 'target':57B 'trust':232C 'typic':182C,224C 'unauthor':141C,160C 'untrust':67B,199C 'user':9A 'vector':250C 'version':81C 'vulner':72C,97C,119C,137C,177C,217C 'web':60B,188C 'well':158C","nicknames":[],"mitigations":[],"who_affected":"Affected deployments are Java clients that run sandboxed Web Start applications or applets loading untrusted internet code and relying on the Java sandbox. Server-side Java that runs only administrator-installed trusted code is not affected according to the description.","tier":"B","verified":{},"analyst_revisit_at":null,"first_public_at":"2026-10-20T22:20:52+00:00","kev":null,"cvss_vector":"CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:N","cvss_by":"secalert_us@oracle.com","poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-91484","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-91484","severity":null,"published_at":"2026-10-20T22:20:52+00:00","modified_at":"2026-10-21T18:44:55+00:00","first_seen_at":"2026-10-23T21:57:27+00:00","fetched_at":"2026-10-23T22:29:00+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"}