{"id":"CVE-2026-91409","kind":"vulnerability","aliases":["CVE-2026-91409"],"related":[],"title":"Oracle Java SE Networking flaw lets remote attackers cause partial denial of service","description":"Vulnerability in Oracle Java SE (component: Networking).   The supported version that is affected is Oracle Java SE: 27. Difficult to exploit vulnerability allows unauthenticated attacker with network access via multiple protocols to compromise Oracle Java SE.  Successful attacks of this vulnerability can result in unauthorized ability to cause a partial denial of service (partial DOS) of Oracle Java SE. Note: This vulnerability can be exploited by using APIs in the specified Component, e.g., through a web service which supplies data to the APIs. This vulnerability also 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. CVSS 3.1 Base Score 3.7 (Availability impacts).  CVSS Vector: (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L).","summary":"A flaw in the Networking component of Oracle Java SE 27 can be triggered over the network by an unauthenticated attacker, who can cause a partial denial of service. Exploitation is difficult, and the description also notes an impact on sandboxed Java Web Start applets that run untrusted code.","severity":"low","cvss":3.7,"epss":0.00259,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["backend","java","oracle-java","runtime","web-services"],"not_affected_if":["no-java-27","no-untrusted-network-input"],"how_to_check":"- Run `java -version` and compare the output against the affected release line Oracle Java SE 27\n- unknown","fix":"- Move Oracle Java SE to a patched release from Oracle's Critical Patch Update advisory for the affected line\n- unknown","status":"open","published_at":"2026-10-20T22:20:44+00:00","first_seen_at":"2026-10-23T21:57:26+00:00","triaged_at":"2026-10-25T04:43:42+00:00","updated_at":"2026-10-25T12:38:52+00:00","category":"runtime","confidence":0.6,"triage":{"at":"2026-10-25T04:43:42Z","model":"claude-haiku-5-5","output":{"fix":"- Move Oracle Java SE to a patched release from Oracle's Critical Patch Update advisory for the affected line\n- unknown","reach":"internet","title":"Oracle Java SE Networking flaw lets remote attackers cause partial denial of service","impact":"low","summary":"A flaw in the Networking component of Oracle Java SE 27 can be triggered over the network by an unauthenticated attacker, who can cause a partial denial of service. Exploitation is difficult, and the description also notes an impact on sandboxed Java Web Start applets that run untrusted code.","category":"runtime","nicknames":[],"who_cares":["java","oracle-java","backend","web-services"],"confidence":0.6,"needs_auth":"no","worst_case":"Partial denial of service against Java SE processes over the network","analyst_note":"","how_to_check":"- Run `java -version` and compare the output against the affected release line Oracle Java SE 27\n- unknown","needs_analyst":false,"not_affected_if":["no-java-27","no-untrusted-network-input"],"who_is_affected":"Teams running Oracle Java SE 27 that expose services which pass untrusted network data into Java networking APIs are the ones to look at. The description also applies to client deployments that run sandboxed Java Web Start or applets loading untrusted code. Teams on other Java versions or without network-facing Java services can likely skip it, though the sources do not list the exact affected builds beyond SE 27.","user_interaction":"no","needs_special_setup":"unknown","severity_if_unknown":"low"},"cost_usd":0.000623,"input_tokens":3552,"output_tokens":535,"severity_before":"low"},"analyst_status":null,"analyst_note":null,"search":"'-2026':15A,18A '-91409':16A,19A '/av':213C '27':39B,95C '3.1':203C,212C '3.7':206C 'abil':123C 'access':105C 'affect':90C 'allow':100C 'also':64B,163C 'api':145C,160C 'applet':73B,180C 'appli':164C 'applic':176C 'attack':8A,49B,102C,115C 'avail':207C 'backend':20B 'base':204C 'caus':9A,52B,125C 'client':170C 'code':77B,186C,188C 'come':190C 'compon':34B,83C,149C 'compromis':110C 'cve':14A,17A 'cvss':202C,209C,211C 'data':157C 'denial':11A,55B,128C 'deploy':167C 'descript':63B 'difficult':60B,96C 'dos':132C 'e.g':150C,187C 'exploit':58B,98C,142C 'flaw':5A,30B 'h/pr':215C 'impact':67B,208C 'internet':193C 'java':2A,21B,24B,37B,70B,81C,93C,112C,135C,166C,173C,179C,198C 'l':221C 'let':6A 'load':182C 'multipl':107C 'n/a':220C 'n/ac':214C 'n/i':219C 'n/s':217C 'n/ui':216C 'network':4A,33B,45B,84C,104C 'note':65B,137C 'oracl':1A,23B,36B,80C,92C,111C,134C 'oracle-java':22B 'partial':10A,54B,127C,131C 'protocol':108C 'reli':195C 'remot':7A 'result':120C 'run':75B,171C,184C 'runtim':25B 'sandbox':69B,172C,178C,199C 'score':205C 'se':3A,38B,82C,94C,113C,136C 'secur':201C 'servic':13A,28B,57B,130C,154C 'specifi':148C 'start':72B,175C 'success':114C 'suppli':156C 'support':86C 'trigger':42B 'typic':168C 'u/c':218C 'unauthent':48B,101C 'unauthor':122C 'untrust':76B,185C 'use':144C 'vector':210C 'version':87C 'via':106C 'vulner':78C,99C,118C,139C,162C 'web':27B,71B,153C,174C 'web-servic':26B","nicknames":[],"mitigations":[],"who_affected":"Teams running Oracle Java SE 27 that expose services which pass untrusted network data into Java networking APIs are the ones to look at. The description also applies to client deployments that run sandboxed Java Web Start or applets loading untrusted code. Teams on other Java versions or without network-facing Java services can likely skip it, though the sources do not list the exact affected builds beyond SE 27.","tier":"C","verified":{},"analyst_revisit_at":null,"first_public_at":"2026-10-20T22:20:44+00:00","kev":null,"cvss_vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L","cvss_by":"secalert_us@oracle.com","poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-91409","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-91409","severity":null,"published_at":"2026-10-20T22:20:44+00:00","modified_at":"2026-10-23T20:17:29+00:00","first_seen_at":"2026-10-23T21:57:26+00:00","fetched_at":"2026-10-23T22:29:00+00:00","note":null},{"source":"epss","external_id":"CVE-2026-91409","url":"https://api.first.org/data/v1/epss?cve=CVE-2026-91409","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"}