CriticalCVE-2015-4852

    Oracle WebLogic Server Deserialization of Untrusted Data Vulnerability (CVE-2015-4852)

    Published In CISA KEV since Sources: CVE.org

    What is affected, what to do

    The WLS Security component in Oracle WebLogic Server 10.3.6.0, 12.1.2.0, 12.1.3.0, and 12.2.1.0 allows remote attackers to execute arbitrary commands via a crafted serialized Java object in T3 protocol traffic to TCP port 7001, related to oracle_common/modules/com.bea.core.apache.commons.collections.jar. NOTE: the scope of this CVE is limited to the WebLogic Server product.

    The vulnerability is being actively exploited; treat it as a priority. The available sources name no fixed version. Check the vendor guidance in the references below. Immediate actions, mitigation and detection rules are in the runbook below.

    Affected
    • Oracle Virtual Desktop Infrastructure lte *..3.5.2
    • Oracle Storagetek Tape Analytics Sw Tool eq 2.3..2.3
    • Oracle WebLogic Server eq 10.3.6.0.0..10.3.6.0.0
    • Oracle WebLogic Server eq 12.1.2.0.0..12.1.2.0.0
    • Oracle WebLogic Server eq 12.1.3.0.0..12.1.3.0.0
    • Oracle WebLogic Server eq 12.2.1.0.0..12.2.1.0.0

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    Metrics

    9.8

    Priority

    XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.

    Source: NVD, CVSS v3

    9.8

    CVSS v3

    Severity Critical on the scale from 0 to 10.

    Source: CVE.org

    95.0 %

    EPSS score

    High — model estimates ≥ 50% chance of real-world exploitation within 30 days.

    Source: FIRST EPSS, percentile 99.86

    Show all metrics
    Severity
    Critical
    Priority (0–325)

    The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?

    Read in glossary
    228.78 Methodology
    Exploit maturity

    An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.

    Read in glossary
    actively exploited
    XIEM Effective CVSS

    XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.

    Read in glossary
    9.8 Methodology
    CVSS v3

    CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.

    Read in glossary
    9.8
    EPSS score

    The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.

    Read in glossary
    95.0 %
    High — model estimates ≥ 50% chance of real-world exploitation within 30 days.
    EPSS percentile

    The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.

    Read in glossary
    99.86
    Critical — this CVE ranks in the top fifth of all CVEs scored today (rank ≥ 80%).
    KEV status

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    Actively exploited
    Published
    In CISA KEV since

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    CISA assessment (SSVC)
    Exploitation: active · automatable · Technical impact: total
    Source: CISA Vulnrichment, as of 4 February 2025
    CWE

    CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.

    Read in glossary
    CWE-502

    Response and mitigation

    Why act now?

    Prioritisation rationale

    This is unauthenticated, network-reachable remote code execution that needs no user interaction and runs code in the context of the WebLogic service. Public exploits, including ysoserial gadget chains, have circulated for years, which places it among the CVEs most likely to be exploited. Attackers mass-scan for open T3 on 7001 and mostly drop coin miners, webshells and botnet loaders. CISA does not flag ransomware use, but a foothold here opens the internal network all the same. Treat every internet-reachable unpatched instance as critical with same-day action. Handle internal-only systems as high priority within days, since legacy versions of this generation typically carry further unpatched deserialization flaws.

    1. Runbook step 1

      Immediate response (0-24 h)

      • Build the inventory: Find every Oracle WebLogic Server 10.3.6.0, 12.1.2.0, 12.1.3.0 and 12.2.1.0 instance, including those embedded in Oracle StorageTek Tape Analytics SW Tool 2.3 and Oracle Virtual Desktop Infrastructure 3.5.2. For each one, check whether TCP 7001/7002 (or other configured listen ports) can be reached from the internet or untrusted segments, using Shodan/Censys lookups on your own ranges and an internal port scan.
      • Patch: Oracle fixed the vulnerability via Security Alert / Critical Patch Update. Patch available from the vendor — look up the exact version in the vendor advisory (My Oracle Support). These release lines are very old, so verify support status and schedule migration to a currently supported WebLogic release if vendor support has lapsed.
      • Block T3/T3S at the perimeter now: Until patched, block inbound T3/T3S on 7001/7002 at the firewall or load balancer for every source except explicitly required admin and application servers. Pure HTTP(S) apps usually don't need T3.
      • Hunt for compromise: Start a compromise assessment on any exposed host. Review the WebLogic JVM process tree, new JSP/WAR files in deployment and tmp directories, cron jobs/scheduled tasks, and outbound connections such as miners or reverse shells.
      • Rotate credentials: If compromise is suspected, isolate the host and take a forensic image. Then rotate WebLogic admin passwords, datasource credentials (from config.xml/boot.properties) and service accounts.

    2. Runbook step 2

      Mitigation layers

      • WebLogic configuration (connection filter): In the Admin Console under Domain → Security → Filter, enable weblogic.security.net.ConnectionFilterImpl. Deny T3/T3S from untrusted sources, e.g. <admin-subnet> * * allow t3 t3s followed by 0.0.0.0/0 * * deny t3 t3s. Restart the server and confirm the filter works with an external T3 handshake test.
      • Network segmentation: Move the admin server and managed servers into a dedicated segment. Restrict their egress to required destinations (database, LDAP) and allow no direct internet access, so attackers can't pull second-stage payloads or open reverse shells.
      • Dedicated admin channel: Bind a separate network channel or administration port to an internal interface only, and disable T3 on the public listener. For web-only apps, publish just HTTP(S) through a fronting reverse proxy.
      • IPS rule: Enable Suricata/Snort signatures for Java deserialization over T3. Match a TCP stream that starts with t3 or contains the serialization magic |ac ed 00 05| alongside class names such as org.apache.commons.collections.functors.InvokerTransformer or ChainedTransformer. Run the rules inline in block mode towards WebLogic.
      • Endpoint hardening: Run WebLogic under an unprivileged service account (never root/SYSTEM). Use EDR, AppLocker or SELinux policy to stop the JVM from spawning shells (cmd.exe, powershell.exe, /bin/sh, bash) or download tools (curl, wget, certutil).

    3. Runbook step 3

      Detection rules

      • EDR/Sysmon process ancestry: Watch Sysmon EID 1 and Windows Event ID 4688 for a java.exe/java parent with weblogic in its command line spawning a shell. KQL: DeviceProcessEvents | where InitiatingProcessFileName =~ "java.exe" and InitiatingProcessCommandLine has "weblogic" and FileName in~ ("cmd.exe","powershell.exe","certutil.exe","bitsadmin.exe"). On Linux, alert on auditd execve where ppid is the WebLogic process and exe is /bin/sh, /bin/bash, /usr/bin/curl or /usr/bin/wget.
      • Network telemetry (Zeek/Suricata): Flag inbound 7001/7002 sessions with a T3 handshake (t3 plus version string) from external or unknown sources. Also flag payloads carrying aced0005 (hex) or rO0AB (Base64) together with Commons Collections class names, which is typical of ysoserial. SPL: index=ids dest_port IN (7001,7002) (signature="*WebLogic*" OR signature="*Java Deserialization*").
      • Egress anomalies: Look for the WebLogic host opening new outbound connections within seconds of inbound T3 traffic: HTTP downloads, unusual ports, mining pools, or DNS queries for rare domains. Correlate via Zeek conn.log over a short time window.
      • Filesystem/logs: Use Sysmon EID 11 or an auditd watch for new .jsp/.war files under servers/*/tmp, autodeploy and application directories. Grep WebLogic server logs for stack traces with InvokerTransformer, ClassCastException or readObject tied to T3 sockets.

    Detection rules

    No NEOSEC detection rule is available for this vulnerability yet.

    Classification under NIS2 and CRA

    Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

    NIS2

    NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.

    Read in glossary
    Actively exploited: treat the vulnerability as a priority in vulnerability handling under Art. 21(2)(e) NIS2. If it is exploited in your environment, check the reporting obligation under Art. 23 (early warning within 24 hours).
    CRA

    The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.

    Read in glossary
    Since 11.09.2026, manufacturers of affected products with digital elements must report actively exploited vulnerabilities under Art. 14 CRA, with an early warning within 24 hours via ENISA's single reporting platform.
    ISO/IEC 27001

    ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.

    Read in glossary
    Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

    Description

    The WLS Security component in Oracle WebLogic Server 10.3.6.0, 12.1.2.0, 12.1.3.0, and 12.2.1.0 allows remote attackers to execute arbitrary commands via a crafted serialized Java object in T3 protocol traffic to TCP port 7001, related to oracle_common/modules/com.bea.core.apache.commons.collections.jar. NOTE: the scope of this CVE is limited to the WebLogic Server product.

    Source: NVD (NIST), cvelistv5, CISA KEV Catalog, CVE.org (MITRE)

    Affected products

    The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

    Affected products
    Affected versionsFixed in
    oraclestoragetek_tape_analytics_sw_tool
    • 2.3
    • —
    oraclevirtual_desktop_infrastructure
    • ≤ 3.5.2
    • —
    oracleweblogic_server
    • 12.1.3.0.0
    • 12.1.2.0.0
    • 12.2.1.0.0
    • 10.3.6.0.0
    • —
    • —
    • —
    • —

    Vendors and products

    Weakness classes (CWE)

    • CWE-502Deserialization of Untrusted Data

      Base

      The product deserializes untrusted data without sufficiently ensuring that the resulting data will be valid.

      Entry at MITRE CWE-502

    Public exploit references

    Publicly reported proof-of-concepts, exploit modules and detection templates for this vulnerability. NEOSEC links to the original sources only and does not provide any exploit code.

    Public exploit references
    CISA KEV CatalogCISA Known Exploited Vulnerability (opens in a new tab)cisa.govactively exploited
    Packet StormOracle Weblogic Server Deserialization Remote Code Execution (opens in a new tab)packetstormsecurity.comPoC (publicly reported)reported, not verified—
    Exploit-DBEDB-ID 42806 (opens in a new tab)exploit-db.comPoC (publicly reported)reported, not verified—
    Exploit-DBEDB-ID 46628 (opens in a new tab)exploit-db.comPoC (publicly reported)reported, not verified—

    References & sources

    • oracle.comtechnetwork/security-advisory/cpujan2018-3236628.htmlx_refsource_CONFIRM, Patch, Vendor advisory
    • oracle.comtechnetwork/security-advisory/cpuapr2017-3236618.htmlx_refsource_CONFIRM, Patch
    • oracle.comtechnetwork/topics/security/cpujan2016-2367955.htmlx_refsource_CONFIRM, Patch, Vendor advisory
    • oracle.comtechnetwork/security-advisory/cpuoct2016-2881722.htmlx_refsource_CONFIRM, Patch, Vendor advisory
    • github.comfoxglovesec/JavaUnserializeExploits/blob/master/weblogic.pyx_refsource_MISC, Product
    • oracle.comtechnetwork/security-advisory/cpuoct2017-3236626.htmlx_refsource_CONFIRM, Patch, Vendor advisory
    • blogs.oracle.comsecurity/entry/security_alert_cve_2015_4852x_refsource_CONFIRM, Broken link
    • securitytracker.com1038292Vulnerability database, x_refsource_SECTRACK, Broken link
    • securityfocus.com77539Vulnerability database, x_refsource_BID, Broken link
    • oracle.comtechnetwork/topics/security/alert-cve-2015-4852-2763333.htmlx_refsource_CONFIRM, Vendor advisory
    • openwall.com[oss-security] 20151117 Re: Assign CVE for common-collections remote code execution on deserialisation flawMailing list, x_refsource_MLIST, Mailing list, Third-party advisory
    • exploit-db.com42806Exploit, x_refsource_EXPLOIT-DB, Exploit, Third-party advisory, Vulnerability database
    • foxglovesecurity.com2015/11/06/what-do-weblogic-websphere-jboss-jenkins-opennms-and…x_refsource_MISC, Exploit
    • packetstormsecurity.comfiles/152268/Oracle-Weblogic-Server-Deserialization-Remote-Code…x_refsource_MISC, Exploit, Third-party advisory, Vulnerability database
    • exploit-db.com46628Exploit, x_refsource_EXPLOIT-DB, Exploit, Third-party advisory, Vulnerability database
    • cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2015-4852government-resource, US government resource
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