CVE-2026-21942 Overview
A denial of service vulnerability exists in the Oracle Solaris product of Oracle Systems, specifically affecting the Filesystems component. This vulnerability allows a low-privileged attacker with local access to the infrastructure where Oracle Solaris executes to cause a complete denial of service condition. The attack requires human interaction from a person other than the attacker to succeed, but once triggered, can result in a hang or frequently repeatable crash of the entire Oracle Solaris system.
Critical Impact
Successful exploitation enables attackers to cause complete denial of service (DoS) of Oracle Solaris systems, potentially disrupting critical business operations and infrastructure availability.
Affected Products
- Oracle Solaris 10
- Oracle Solaris 11
Discovery Timeline
- January 20, 2026 - CVE-2026-21942 published to NVD
- January 21, 2026 - Last updated in NVD database
Technical Details for CVE-2026-21942
Vulnerability Analysis
This vulnerability is classified as a Resource Exhaustion issue (CWE-400: Uncontrolled Resource Consumption) within the Filesystems component of Oracle Solaris. The flaw allows an authenticated local attacker to trigger conditions that lead to system instability, resulting in either a system hang or a repeatable crash condition.
The vulnerability specifically impacts availability without affecting confidentiality or integrity of the system. While the attack requires local access and low-level privileges, the requirement for human interaction from another user suggests a social engineering component may be necessary for successful exploitation.
Root Cause
The root cause is identified as CWE-400 (Uncontrolled Resource Consumption), indicating that the Filesystems component fails to properly limit resource allocation or consumption. This allows an attacker to exhaust system resources through specially crafted filesystem operations, ultimately leading to a denial of service condition affecting the entire Oracle Solaris operating system.
Attack Vector
The attack vector for CVE-2026-21942 is local in nature, requiring the attacker to have authenticated access to the Oracle Solaris system. The exploitation path involves:
- The attacker must first obtain low-privileged access to the target Oracle Solaris system
- Human interaction from a different user is required to trigger the vulnerable condition
- Once triggered, the attacker can cause resource exhaustion in the Filesystems component
- The exploitation results in a complete system hang or repeatable crash
The requirement for human interaction suggests the attack may involve manipulating filesystem objects that another user must access, or leveraging shared filesystem resources in a way that triggers the vulnerability when accessed by a legitimate user.
Detection Methods for CVE-2026-21942
Indicators of Compromise
- Unusual filesystem operation patterns or excessive filesystem-related system calls from low-privileged accounts
- Unexpected system hangs or crashes with filesystem component involvement in crash dumps
- Abnormal resource consumption patterns in filesystem subsystems
- Repeated system instability events correlated with specific user activity on shared filesystem resources
Detection Strategies
- Monitor system logs for filesystem-related errors or warnings preceding system crashes
- Implement audit logging for filesystem operations from non-administrative accounts
- Configure watchdog timers to detect and alert on system hangs
- Use kernel-level monitoring tools to track resource consumption in the Filesystems component
Monitoring Recommendations
- Enable comprehensive audit logging on Oracle Solaris systems to track filesystem operations
- Deploy system health monitoring to detect abnormal resource consumption patterns
- Configure automated alerting for system hang or crash events
- Implement centralized log collection to correlate filesystem-related events across multiple systems
How to Mitigate CVE-2026-21942
Immediate Actions Required
- Review and apply the Oracle Critical Patch Update (CPU) for January 2026 immediately
- Audit user accounts with local access to identify potential threat actors
- Implement the principle of least privilege to minimize accounts with local system access
- Enable enhanced monitoring on Oracle Solaris systems running versions 10 and 11
Patch Information
Oracle has addressed this vulnerability in the January 2026 Critical Patch Update. Administrators should consult the Oracle Security Alert January 2026 for detailed patching instructions and download the appropriate patches for Oracle Solaris versions 10 and 11.
Workarounds
- Restrict local access to Oracle Solaris systems to only essential personnel
- Implement additional access controls on shared filesystem resources
- Consider network segmentation to limit exposure of affected systems
- Enable resource quotas and limits where applicable to mitigate resource exhaustion attacks
# Example: Enable filesystem auditing on Oracle Solaris
# Verify current audit configuration
auditconfig -getpolicy
# Enable filesystem operation auditing
auditconfig -setpolicy +argv,arge
audit -s
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
