{"id":"CVE-2026-91463","kind":"vulnerability","aliases":["CVE-2026-91463"],"related":[],"title":"Oracle Java SE: JGSS flaw exposes data to unauthenticated network attackers","description":"Vulnerability in the Oracle Java SE, Oracle GraalVM for JDK, Oracle GraalVM Enterprise Edition product of Oracle Java SE (component: JGSS).  Supported versions that are affected are Oracle Java SE: 8u503, 8u503-perf, 11.0.32.1, 17.0.20.1, 21.0.12.1, 25.0.4.1, 27; Oracle GraalVM for JDK: 17.0.20.1 and  21.0.12.1; Oracle GraalVM Enterprise Edition: 21.3.19.1.1. Difficult to exploit vulnerability allows unauthenticated attacker with network access via multiple protocols to compromise Oracle Java SE, Oracle GraalVM for JDK, Oracle GraalVM Enterprise Edition.  Successful attacks require human interaction from a person other than the attacker. Successful attacks of this vulnerability can result in  unauthorized access to critical data or complete access to all Oracle Java SE, Oracle GraalVM for JDK, Oracle GraalVM Enterprise Edition 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 5.3 (Confidentiality impacts).  CVSS Vector: (CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:N/A:N).","summary":"A flaw in the JGSS component of Oracle Java SE and GraalVM lets an unauthenticated remote attacker reach data the runtime can access. Exploitation is hard and needs a victim to take an action, and the Oracle note says the risk is mainly for clients running untrusted Java Web Start or applet code.","severity":"medium","cvss":5.3,"epss":0.00227,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["client-desktops","graalvm","java","jgss","runtime"],"not_affected_if":["no-untrusted-applets-or-web-start","server-only-trusted-code"],"how_to_check":"- Run `java -version` and compare the build with the affected versions listed in the sources (8u503, 11.0.32.1, 17.0.20.1, 21.0.12.1, 25.0.4.1, 27).\n- Check whether the GraalVM for JDK or GraalVM Enterprise Edition builds in use match `17.0.20.1`, `21.0.12.1` or `21.3.19.1.1`.","fix":"- Move Oracle Java SE to a patched release from Oracle's April 2026 critical patch update (the sources do not list the exact fixed build).\n- Move GraalVM for JDK or GraalVM Enterprise Edition to a patched release from the same update.","status":"open","published_at":"2026-10-20T22:20:49+00:00","first_seen_at":"2026-10-23T21:57:27+00:00","triaged_at":"2026-10-25T04:22:32+00:00","updated_at":"2026-10-25T12:38:52+00:00","category":"runtime","confidence":0.6,"triage":{"at":"2026-10-25T04:22:32Z","model":"claude-haiku-5-5","output":{"fix":"- Move Oracle Java SE to a patched release from Oracle's April 2026 critical patch update (the sources do not list the exact fixed build).\n- Move GraalVM for JDK or GraalVM Enterprise Edition to a patched release from the same update.","reach":"internet","title":"Oracle Java SE: JGSS flaw exposes data to unauthenticated network attackers","impact":"high","summary":"A flaw in the JGSS component of Oracle Java SE and GraalVM lets an unauthenticated remote attacker reach data the runtime can access. Exploitation is hard and needs a victim to take an action, and the Oracle note says the risk is mainly for clients running untrusted Java Web Start or applet code.","category":"runtime","nicknames":[],"who_cares":["java","graalvm","jgss","client-desktops"],"confidence":0.6,"needs_auth":"no","worst_case":"Attacker reads critical data accessible to the Java runtime","analyst_note":"Confirm the fixed Java build numbers in Oracle's April 2026 CPU advisory and whether server-side Java deployments are actually affected.","how_to_check":"- Run `java -version` and compare the build with the affected versions listed in the sources (8u503, 11.0.32.1, 17.0.20.1, 21.0.12.1, 25.0.4.1, 27).\n- Check whether the GraalVM for JDK or GraalVM Enterprise Edition builds in use match `17.0.20.1`, `21.0.12.1` or `21.3.19.1.1`.","needs_analyst":true,"not_affected_if":["server-only-trusted-code","no-untrusted-applets-or-web-start"],"who_is_affected":"The sources say the issue applies to Java deployments that run untrusted code and rely on the Java sandbox, such as sandboxed Java Web Start applications or applets on client machines. The sources say it does not apply to server deployments that run only trusted code installed by an administrator.","user_interaction":"yes","needs_special_setup":"unknown","severity_if_unknown":"unknown"},"cost_usd":0.000739,"input_tokens":3829,"output_tokens":713,"severity_before":"medium"},"analyst_status":null,"analyst_note":null,"search":"'-2026':13A,16A '-91463':14A,17A '/av':274C '11.0.32.1':112C '17.0.20.1':113C,121C '21.0.12.1':114C,123C '21.3.19.1.1':128C '25.0.4.1':115C '27':116C '3.1':264C,273C '5.3':267C '8u503':108C,110C '8u503-perf':109C 'access':47B,138C,176C,182C,196C 'action':58B 'administr':262C 'affect':103C 'allow':133C 'applet':76B,217C 'appli':201C,243C 'applic':213C 'attack':11A,41B,135C,156C,166C,168C 'base':265C 'client':19B,69B,207C 'client-desktop':18B 'code':77B,223C,225C,256C,258C 'come':227C 'complet':181C 'compon':30B,97C 'compromis':143C 'confidenti':268C 'critic':178C 'cve':12A,15A 'cvss':263C,270C,272C 'data':7A,43B,179C,197C 'deploy':204C,246C 'desktop':20B 'difficult':129C 'e.g':224C,257C 'edit':91C,127C,154C,195C 'enterpris':90C,126C,153C,194C 'exploit':48B,131C 'expos':6A 'flaw':5A,26B 'graalvm':21B,36B,85C,89C,118C,125C,148C,152C,189C,193C 'h/i':280C 'h/pr':276C 'hard':50B 'human':158C 'impact':269C 'instal':259C 'interact':159C 'internet':230C 'java':2A,22B,33B,72B,82C,95C,106C,145C,186C,203C,210C,216C,235C,245C 'jdk':87C,120C,150C,191C 'jgss':4A,23B,29B,98C 'let':37B 'load':219C,251C 'main':67B 'multipl':140C 'n':282C 'n/a':281C 'n/ac':275C 'n/ui':277C 'need':52B 'network':10A,137C 'note':62B,198C 'oracl':1A,32B,61B,81C,84C,88C,94C,105C,117C,124C,144C,147C,151C,185C,188C,192C 'perf':111C 'person':162C 'product':92C 'protocol':141C 'r/s':278C 'reach':42B 'reli':232C 'remot':40B 'requir':157C 'result':173C 'risk':65B 'run':70B,208C,221C,253C 'runtim':24B,45B 'sandbox':209C,215C,236C 'say':63B 'score':266C 'se':3A,34B,83C,96C,107C,146C,187C 'secur':238C 'server':249C 'start':74B,212C 'success':155C,167C 'support':99C 'take':56B 'trust':255C 'typic':205C,247C 'u/c':279C 'unauthent':9A,39B,134C 'unauthor':175C 'untrust':71B,222C 'vector':271C 'version':100C 'via':139C 'victim':54B 'vulner':78C,132C,171C,200C,240C 'web':73B,211C","nicknames":[],"mitigations":[],"who_affected":"The sources say the issue applies to Java deployments that run untrusted code and rely on the Java sandbox, such as sandboxed Java Web Start applications or applets on client machines. The sources say it does not apply to server deployments that run only trusted code installed by an administrator.","tier":"C","verified":{},"analyst_revisit_at":null,"first_public_at":"2026-10-20T22:20:49+00:00","kev":null,"cvss_vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:N/A:N","cvss_by":"secalert_us@oracle.com","poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-91463","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-91463","severity":null,"published_at":"2026-10-20T22:20:49+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},{"source":"epss","external_id":"CVE-2026-91463","url":"https://api.first.org/data/v1/epss?cve=CVE-2026-91463","severity":null,"published_at":null,"modified_at":null,"first_seen_at":"2026-10-25T12:38:52+00:00","fetched_at":"2026-10-25T12:38:52+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"}