CVE-2025-30733 Overview
CVE-2025-30733 is an authentication-related vulnerability [CWE-287] in the RDBMS Listener component of Oracle Database Server. The flaw allows an unauthenticated attacker with network access via Oracle Net to compromise the RDBMS Listener. Successful exploitation requires human interaction from a person other than the attacker. The vulnerability impacts confidentiality, granting unauthorized access to critical data accessible through the RDBMS Listener. Public technical analysis links the issue to a memory leak in the Oracle Transparent Network Substrate (TNS) protocol handling. Affected versions span Oracle Database 19.3-19.26, 21.3-21.17, and 23.4-23.7.
Critical Impact
Unauthenticated network attackers can extract sensitive memory contents from the Oracle RDBMS Listener, exposing critical data accessible to the listener process.
Affected Products
- Oracle Database Server RDBMS Listener versions 19.3 through 19.26
- Oracle Database Server RDBMS Listener versions 21.3 through 21.17
- Oracle Database Server RDBMS Listener versions 23.4 through 23.7
Discovery Timeline
- 2025-04-15 - Oracle releases security patch as part of the April 2025 Critical Patch Update
- 2025-04-15 - CVE-2025-30733 published to NVD
- 2025-05-19 - Last updated in NVD database
Technical Details for CVE-2025-30733
Vulnerability Analysis
The vulnerability resides in the Oracle RDBMS Listener, the network endpoint that brokers client connections to Oracle Database instances over the Oracle Net (TNS) protocol. The listener handles connection requests on TCP port 1521 by default. According to public technical analysis, the flaw manifests as a memory leak triggered through specially crafted TNS protocol messages. An attacker reachable over the network can interact with the listener and recover residual memory contents from the listener process. These contents may include connection strings, credentials in transit, query fragments, or other data the listener has handled. The CWE-287 classification reflects improper authentication of the protocol exchange that enables this disclosure without valid credentials.
Root Cause
The root cause is improper handling of authentication state within Oracle Net packet processing in the RDBMS Listener. Crafted protocol messages cause the listener to return uninitialized or previously used memory in its responses. Because the listener processes requests before authentication is fully established, the disclosure path is reachable to unauthenticated clients.
Attack Vector
The attack is remote and requires only network reachability to the listener port. The CVSS vector includes a user interaction requirement, indicating that a person other than the attacker must perform an action for full compromise. An attacker probes the listener with crafted TNS packets and parses the responses for leaked memory fragments. Refer to the Driftnet blog analysis on Oracle TNS memory leak for protocol-level details and the Oracle April 2025 Critical Patch Update advisory for vendor guidance.
Detection Methods for CVE-2025-30733
Indicators of Compromise
- Unusual volumes of TNS connection attempts to TCP port 1521 from unexpected sources without progressing to authenticated sessions.
- Repeated malformed or atypically sized Oracle Net packets logged by the listener.
- listener.log entries showing high rates of incomplete handshakes or unusual CONNECT_DATA strings.
Detection Strategies
- Monitor the Oracle listener log for anomalous connection patterns, including bursts of dropped or partial TNS sessions from a single source.
- Deploy network IDS signatures that flag malformed Oracle Net packets and unauthenticated probing of port 1521.
- Correlate listener telemetry with firewall logs to identify external sources reaching the listener that should not have access.
Monitoring Recommendations
- Forward listener.log and alert.log to a centralized analytics platform and baseline normal client behavior.
- Alert on connections to the listener from networks outside the documented application tier.
- Track process memory and handle growth on the listener host to identify abnormal interaction patterns.
How to Mitigate CVE-2025-30733
Immediate Actions Required
- Apply the April 2025 Oracle Critical Patch Update to all affected Oracle Database installations.
- Restrict network access to TCP port 1521 so only authorized application servers can reach the listener.
- Audit listener exposure on internet-facing and untrusted network segments and remove unnecessary reachability.
Patch Information
Oracle addressed CVE-2025-30733 in the April 2025 Critical Patch Update covering Oracle Database 19.3-19.26, 21.3-21.17, and 23.4-23.7. Apply the corresponding Database Release Update or Patch Set Update from the Oracle Security Advisory April 2025. Validate patch level using opatch lsinventory after installation.
Workarounds
- Enforce IP-based access control with tcp.validnode_checking, tcp.invited_nodes, and tcp.excluded_nodes in sqlnet.ora to limit which hosts may contact the listener.
- Place the listener behind a firewall or service mesh that permits only documented application clients.
- Enable Oracle Native Network Encryption and integrity checking to reduce the value of any data observable on the wire.
# Configuration example: restrict listener access in sqlnet.ora
tcp.validnode_checking = yes
tcp.invited_nodes = (10.0.10.21, 10.0.10.22, 10.0.10.23)
tcp.excluded_nodes = (0.0.0.0/0)
# Verify applied patches after CPU April 2025 installation
$ORACLE_HOME/OPatch/opatch lsinventory | grep -i "April 2025"
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
