{"id":"CVE-2026-83378","kind":"vulnerability","aliases":["CVE-2026-83378"],"related":[],"title":"Oracle Java SE: compiler flaw lets remote attackers change some data","description":"Vulnerability in Oracle Java SE (component: Compiler).  Supported versions that are affected are Oracle Java SE: 21.0.12.1, 25.0.4.1 and  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 update, insert or delete access to some of Oracle Java SE accessible data as well as  unauthorized read access to a subset of Oracle Java SE accessible data. Note: This vulnerability can only be exploited by supplying data to APIs in the specified Component without using Untrusted Java Web Start applications or Untrusted Java applets, such as through a web service. CVSS 3.1 Base Score 4.8 (Confidentiality and Integrity impacts).  CVSS Vector: (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N).","summary":"A flaw in the Java SE Compiler component lets an unauthenticated attacker over the network read and modify a subset of data that Java SE can reach, by supplying crafted data to APIs such as through a web service. Exploitation is difficult, and the sources rate it CVSS 4.8 medium with no confidentiality or integrity loss beyond a subset of data.","severity":"medium","cvss":4.8,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["java","oracle-jdk","runtime","self-hosted","web-services"],"not_affected_if":["default-config"],"how_to_check":"- Run `java -version` and compare against the affected releases 21.0.12.1, 25.0.4.1 and 27.\n- Check whether the application runs on an Oracle Java SE build listed as affected.","fix":"- Move Oracle Java SE to a patched release from the April 2026 Critical Patch Update (exact fixed versions: unknown in the sources).","status":"open","published_at":"2026-10-20T22:19:54+00:00","first_seen_at":"2026-10-23T21:57:25+00:00","triaged_at":"2026-10-25T04:33:17+00:00","updated_at":"2026-10-25T04:33:17+00:00","category":"runtime","confidence":0.6,"triage":{"at":"2026-10-25T04:33:17Z","model":"claude-haiku-5-5","output":{"fix":"- Move Oracle Java SE to a patched release from the April 2026 Critical Patch Update (exact fixed versions: unknown in the sources).","reach":"network","title":"Oracle Java SE: compiler flaw lets remote attackers change some data","impact":"medium","summary":"A flaw in the Java SE Compiler component lets an unauthenticated attacker over the network read and modify a subset of data that Java SE can reach, by supplying crafted data to APIs such as through a web service. Exploitation is difficult, and the sources rate it CVSS 4.8 medium with no confidentiality or integrity loss beyond a subset of data.","category":"runtime","nicknames":[],"who_cares":["java","oracle-jdk","web-services","self-hosted"],"confidence":0.6,"needs_auth":"no","worst_case":"Attacker reads and changes a subset of data the Java application can access","analyst_note":"Check the Oracle Critical Patch Update advisory for the exact fixed Java SE builds and which APIs in the Compiler component are reachable.","how_to_check":"- Run `java -version` and compare against the affected releases 21.0.12.1, 25.0.4.1 and 27.\n- Check whether the application runs on an Oracle Java SE build listed as affected.","needs_analyst":true,"not_affected_if":["default-config"],"who_is_affected":"Any service that runs Oracle Java SE 21.0.12.1, 25.0.4.1 or 27 and passes untrusted data into the affected compiler APIs, for example a web service. The sources say untrusted Java Web Start applications and applets are not needed for exploitation. Teams that run no Oracle Java SE builds in these versions can skip it.","user_interaction":"no","needs_special_setup":"unknown","severity_if_unknown":"medium"},"cost_usd":0.000666,"input_tokens":3542,"output_tokens":623,"severity_before":"medium"},"analyst_status":null,"analyst_note":null,"search":"'-2026':13A,16A '-83378':14A,17A '/av':211C '21.0.12.1':106C '25.0.4.1':107C '27':109C '3.1':199C,210C '4.8':77B,202C 'access':119C,141C,148C,155C,163C 'affect':101C 'allow':114C 'api':61B,176C 'applet':191C 'applic':187C 'attack':8A,40B,116C,129C 'base':200C 'beyond':85B 'chang':9A 'compil':4A,35B,96C 'compon':36B,95C,180C 'compromis':124C 'confidenti':81B,203C 'craft':58B 'cve':12A,15A 'cvss':76B,198C,207C,209C 'data':11A,50B,59B,89B,149C,164C,174C 'delet':140C 'difficult':70B,110C 'exploit':68B,112C,171C 'flaw':5A,30B 'h/pr':213C 'host':25B 'impact':206C 'insert':138C 'integr':83B,205C 'java':2A,18B,33B,52B,93C,104C,126C,146C,161C,184C,190C 'jdk':21B 'l/a':218C 'l/i':217C 'let':6A,37B 'loss':84B 'medium':78B 'modifi':46B 'multipl':121C 'n':219C 'n/ac':212C 'n/s':215C 'n/ui':214C 'network':43B,118C 'note':165C 'oracl':1A,20B,92C,103C,125C,145C,160C 'oracle-jdk':19B 'protocol':122C 'rate':74B 'reach':55B 'read':44B,154C 'remot':7A 'result':134C 'runtim':22B 'score':201C 'se':3A,34B,53B,94C,105C,127C,147C,162C 'self':24B 'self-host':23B 'servic':28B,67B,197C 'sourc':73B 'specifi':179C 'start':186C 'subset':48B,87B,158C 'success':128C 'suppli':57B,173C 'support':97C 'u/c':216C 'unauthent':39B,115C 'unauthor':136C,153C 'untrust':183C,189C 'updat':137C 'use':182C 'vector':208C 'version':98C 'via':120C 'vulner':90C,113C,132C,167C 'web':27B,66B,185C,196C 'web-servic':26B 'well':151C 'without':181C","nicknames":[],"mitigations":[],"who_affected":"Any service that runs Oracle Java SE 21.0.12.1, 25.0.4.1 or 27 and passes untrusted data into the affected compiler APIs, for example a web service. The sources say untrusted Java Web Start applications and applets are not needed for exploitation. Teams that run no Oracle Java SE builds in these versions can skip it.","tier":"C","verified":{},"analyst_revisit_at":null,"first_public_at":"2026-10-20T22:19:54+00:00","kev":null,"cvss_vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N","cvss_by":"secalert_us@oracle.com","poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-83378","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-83378","severity":null,"published_at":"2026-10-20T22:19:54+00:00","modified_at":"2026-10-21T18:44:19+00:00","first_seen_at":"2026-10-23T21:57:25+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"}