Oracle WebLogic Server: Unauthenticated remote takeover via T3 and IIOP
Summary
Oracle WebLogic Server (Core component, Oracle Fusion Middleware) contains a critical flaw that allows an unauthenticated attacker with network access to the T3 or IIOP protocol to compromise the server. Successful exploitation can lead to full takeover of the server, with high impact on confidentiality, integrity and availability (CVSS 3.1 base score 9.8). No credentials or user interaction are required, so internet-reachable WebLogic instances are at the highest risk. Oracle addressed the issue in its October 2026 Critical Patch Update.
Affected
- Oracle WebLogic Server 12.2.1.4.0
- Oracle WebLogic Server 14.1.1.0.0
- Oracle WebLogic Server 14.1.2.0.0
- Oracle WebLogic Server 15.1.1.0.0
Fixed in
Unknown. Oracle addressed the vulnerability in the October 2026 Critical Patch Update (published 20 October 2026). Patch numbers per release line are listed in the Patch Availability table of the advisory.
Workaround
- Applying the patch is the fix; no Oracle-published interim workaround was found.
- Block access to T3 (default port 7001) and IIOP from untrusted networks, and verify this against the advisory before relying on it.
Exploitation
- Oracle does not state that the vulnerability is exploited.
- Not listed in the CISA KEV catalogue at the time of research (30 October 2026).
- No public proof of concept found; this does not prove that none exists.
Our recommendation
- Inventory all WebLogic Server instances, including those in vendor-hosted or third-party applications.
- Check whether T3 and IIOP are reachable from the internet and restrict them to trusted networks immediately.
- Apply the October 2026 Oracle CPU patch for your release line, within one week for internet-facing systems.
- Review the other October 2026 WebLogic and SOA Suite flaws, for example CVE-2026-91323.
- Monitor the CISA KEV catalogue and the vendor advisory for updates.
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- Oracle Security Alert: Critical Patch Update October 2026 www.oracle.com
- NVD record via Vulners: CVE-2026-83399 vulners.com
- Strix CVE summary: CVE-2026-83399 www.strix.ai
- Brandefense: Oracle October 2026 Critical Patch Update brandefense.io
- ThreatFrontier: Oracle October 2026 CPU threatfrontier.com
- SecurityOnline: Oracle Fusion Middleware vulnerabilities October 2026 securityonline.info
Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 30 Oct 2026, 17:17.
Original description (NVD)
Vulnerability in the Oracle WebLogic Server product of Oracle Fusion Middleware (component: Core). Supported versions that are affected are 12.2.1.4.0, 14.1.1.0.0, 14.1.2.0.0 and 15.1.1.0.0. Easily exploitable vulnerability allows unauthenticated attacker with network access via T3, IIOP to compromise Oracle WebLogic Server. Successful attacks of this vulnerability can result in takeover of Oracle WebLogic Server. CVSS 3.1 Base Score 9.8 (Confidentiality, Integrity and Availability impacts). CVSS Vector: (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H).
NVD references (1)
Sources
The tracker combines official, freely usable data sources – updated continuously:
- NVD (NIST) – CVEs, rating (CVSS), affected products
- CISA KEV – vulnerabilities confirmed by CISA as actively exploited
- CISA Vulnrichment – CISA assessment (SSVC) in the official CVE record
- FIRST EPSS – probability of exploitation
- Microsoft MSRC – Patch Tuesday: vulnerabilities, severity, updates
- PoC-in-GitHub – public proof-of-concept repositories
- Metasploit (Rapid7) – modules of the Metasploit Framework
- Exploit-DB (OffSec) – archive of public exploits (links only)
- Patch days: official vendor pages (linked per vendor) (Vendor patch days)
This product uses data from the NVD API but is not endorsed or certified by the NVD. EPSS data © FIRST.org.
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