CVE-2023-21839
CVE-2023-21839 is a security flaw in Oracle WebLogic Server, Oracle’s server for running business applications. Attackers are using a flaw in Oracle WebLogic Server that its maker hasn't described in detail. The US Cybersecurity and Infrastructure Security Agency (CISA) added it to its catalog of flaws known to be used in attacks on 1 May 2023.[1]
Oracle WebLogic Server is business software or equipment. Most families won’t have it, but attackers break into it to get inside companies, and from there to what those companies hold about their customers, patients and staff. Oracle has published a fix or advice.
Description
CISA calls it an unspecified in Oracle WebLogic Server. In its words: “Oracle WebLogic Server contains an unspecified vulnerability that allows an unauthenticated attacker with network access via T3, IIOP, to compromise Oracle WebLogic Server.”[1]
The CVE record adds: “Vulnerability in the Oracle WebLogic Server product of Oracle Fusion Middleware (component: Core). Supported versions that are affected are 12.2.1.3.0, 12.2.1.4.0 and 14.1.1.0.0. 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 unauthorized access to critical data or complete access to all Oracle WebLogic Server accessible data. CVSS 3.1 Base Score 7.5 (Confidentiality impacts). CVSS Vector: (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N).”[2]
The underlying weakness is deserialization of untrusted data (CWE-502), missing authentication (CWE-306), in MITRE’s list of common software weaknesses.
It scores 7.5 out of 10 on the Common Vulnerability Scoring System, which rates it high, scored by the organisation that published the CVE using CVSS 3.1.[2]
Affected versions
NVD’s record doesn’t list version ranges for it; Oracle’s advisory has them[3]. CISA names the product as Oracle WebLogic Server.
Most families won’t have Oracle WebLogic Server; it’s for whoever looks after IT at work.
Exploitation
CISA added it to its catalog of known exploited vulnerabilities on 1 May 2023, 103 days after it was made public. CISA lists a flaw only when it has reliable evidence of it being exploited, and gave US federal agencies until 22 May 2023 to fix it.[1]
FIRST’s Exploit Prediction Scoring System, which estimates how likely a flaw is to be used in attacks in the next 30 days from what it sees across the internet, puts it at over 99%. That’s in the top 1% of the flaws it scores.[4]
CISA assesses it as automatable: attackers can run it against many targets at once.
CISA doesn’t say who was attacked, or how.
Fix
Oracle has published a fix or advice.[3] CISA’s required action: “Apply updates per vendor instructions.”[1]
- Check whether you use it.Oracle WebLogic Server is business software or equipment, so most families won’t have it. If you run a business, or work from home on company equipment, ask whoever looks after your IT.
- Send this page to your IT person.Ask them to confirm it’s fixed, or not in use. CISA gave US government agencies until 22 May 2023 to fix it.
- If it can’t be fixed, take it offline.CISA’s advice when there’s no fix is to stop using the product, or take it off the internet, until there is one.
You can’t fix someone else’s server, but you can watch for what follows a break-in like this: a breach notice, a password reset you didn’t ask for, or a scam message that knows things it shouldn’t. HARD watches for those for you and your family.
Timeline
| Date | Event |
|---|---|
| The flaw is made public in the National Vulnerability Database, with a severity score of 7.5.[2] | |
| CISA adds it to its catalog of flaws known to be used in attacks.[1] | |
| CISA’s deadline for US government agencies to fix it.[1] | |
| FIRST puts the odds of it being used in attacks in the next 30 days at over 99%.[4] |
See also
Other Oracle WebLogic Server flaws
- CVE-2024-21182: unspecified ·
- CVE-2020-2883: unspecified ·
- CVE-2020-14644: remote code execution ·
- CVE-2017-3506: OS command injection ·
- CVE-2018-2628: unspecified ·
- CVE-2017-10271: corporation webLogic server remote code execution ·
Other Oracle flaws
- CVE-2026-21962, Oracle HTTP Server and Oracle Weblogic Server Proxy Plug-in: improper access control ·
- CVE-2026-46817, Oracle E-Business Suite: improper privilege management ·
- CVE-2026-35273, Oracle PeopleSoft Enterprise PeopleTools: missing authentication for critical function ·
- CVE-2025-61757, Oracle Fusion Middleware: missing authentication for critical function ·
- CVE-2025-61884, Oracle E-Business Suite: server-side request forgery (SSRF) ·
Other deserialization of untrusted data flaws
- CVE-2021-23758, Ajax.NET Professional: deserialization of untrusted data ·
- CVE-2026-63077, JetBrains TeamCity: deserialization of untrusted data ·
- CVE-2026-50522, Microsoft SharePoint: deserialization of untrusted data ·
- CVE-2026-58644, Microsoft SharePoint: deserialization of untrusted data ·
- CVE-2026-45659, Microsoft SharePoint Server: deserialization of untrusted data ·
Added the same day
- CVE-2023-1389, TP-Link Archer AX21: archer AX-21 command injection ·
- CVE-2021-45046, Apache Log4j2: deserialization of untrusted data ·
Every Oracle flaw on CISA’s list · Everything added in May 2023
References
- ^ Cybersecurity and Infrastructure Security Agency. “Oracle WebLogic Server Unspecified Vulnerability”. Known Exploited Vulnerabilities Catalog, added 1 May 2023.
- ^ National Institute of Standards and Technology. “CVE-2023-21839 Detail”. National Vulnerability Database, published 18 Jan 2023.
- ^ Oracle. Advisories and fixes: oracle.com.
- ^ FIRST. “Exploit Prediction Scoring System”. EPSS 0.999, percentile 100.0, 31 Oct 2026.
- CVE Program. “CVE-2023-21839”. The official CVE record.
This article is built from CISA’s catalog (version 2026.10.30), NVD’s record and FIRST’s scores, kept in HARD’s database and checked every morning. The plain English is HARD’s.