CVE-2026-91479 in Database Server
Summary
by MITRE • 10/21/2026
Vulnerability in the RDBMS component of Oracle Database Server. Supported versions that are affected are 23.4.0-23.26.3. Easily exploitable vulnerability allows unauthenticated attacker with access to the physical communication segment attached to the hardware where the RDBMS executes to compromise RDBMS. Successful attacks of this vulnerability can result in unauthorized ability to cause a hang or frequently repeatable crash (complete DOS) of RDBMS. CVSS 3.1 Base Score 6.5 (Availability impacts). CVSS Vector: (CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H).
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Analysis
by VulDB Data Team • 10/21/2026
The identified vulnerability resides within the Relational Database Management System component of Oracle Database Server, specifically affecting supported versions ranging from 23.4.0 to 23.26.3. This flaw represents a significant security risk due to its potential for causing complete denial of service conditions against critical database infrastructure. The nature of this vulnerability is characterized by an easily exploitable condition that does not require authentication or user interaction, thereby lowering the barrier for malicious actors seeking to disrupt services.
The attack vector associated with this vulnerability is classified as adjacent network access rather than local or remote over the internet. This means that an attacker must have physical or logical access to the same communication segment attached to the hardware where the Oracle RDBMS executes. While this restricts the pool of potential attackers compared to remotely exploitable flaws, it remains a serious concern for environments where internal networks are not strictly segmented or where unauthorized devices can be connected to the server's network interface. The requirement for access to the physical communication segment implies that threats may originate from compromised hosts on the same subnet, rogue devices plugged into switch ports, or insider threats with local network connectivity.
Upon successful exploitation, an attacker gains the ability to cause a hang or trigger frequently repeatable crashes of the RDBMS process. This results in a complete denial of service, effectively rendering the database unavailable for legitimate users and applications. The impact is strictly on availability, as indicated by the CVSS 3.1 base score of 6.5 with high severity for availability impacts. There are no reported implications for confidentiality or integrity within this specific vulnerability description; however, the loss of availability can have cascading effects on business operations dependent on real-time data access and transaction processing.
From a classification perspective, this vulnerability aligns with CWE-400, which covers uncontrolled resource consumption leading to denial of service conditions. The exploitation technique likely involves sending malformed or specially crafted packets that exhaust system resources such as memory, CPU cycles, or connection handles within the RDBMS engine, causing it to become unresponsive or crash repeatedly. In terms of adversary tactics, this aligns with MITRE ATT&CK techniques related to Denial of Service, specifically those focusing on resource exhaustion via network-based attacks. The lack of authentication requirements places this in a category similar to CWE-287 regarding improper authentication, although the primary impact is service disruption rather than unauthorized access.
Mitigation strategies should focus primarily on network segmentation and strict access control lists applied at the switch or firewall level adjacent to the database servers. Administrators must ensure that only authorized application servers and management stations can communicate with the Oracle RDBMS instance over this specific communication segment. Implementing intrusion detection systems capable of identifying anomalous traffic patterns associated with resource exhaustion attacks is also recommended. Furthermore, applying the latest security patches provided by Oracle for versions 23.4.0 through 23.26.3 is critical to resolving the underlying code flaw that permits such exploitation. Regular auditing of network access policies and monitoring database server health metrics can help in early detection and prevention of potential denial-of-service events stemming from this vulnerability.