In the Linux kernel, a vulnerability has been resolved regarding the vsock functionality. Specifically, this vulnerability allows for a null pointer dereference in the vsock_has_data and vsock_has_space functions. This issue arises when a vsock socket has been de-assigned from a transport, which should not occur.
The vulnerability, identified as CVE-2025-21666, has a CVSS score of 5.5, categorizing it as medium severity. The potential impact is significant, particularly regarding availability, where the code could lead to high availability impact if exploited. Organizations running vulnerable versions of the Linux kernel should take immediate action.
Recent reports indicate that while prior commits aimed to resolve underlying issues, the risk of encountering similar problems remains. The safeguard implemented now allows the system to return a warning alongside a zero value for data availability, maintaining a more stable operational state.
Organizations should prioritize patching immediately. The urgency stems from the potential for service disruption and the need to uphold system integrity and availability.
Vulnerability Details
The CVE-2025-21666 vulnerability has been officially described as follows: In the Linux kernel, the issue arises within the vsock functionality, specifically in functions that check for data presence and availability. The vulnerability is linked to a null pointer dereference issue, which can lead to a crash or unpredictable behavior of the application.
The CVSS score for this vulnerability is 5.5, indicating a medium severity level. This score reflects the local attack vector, low complexity, and low privileges required to exploit the vulnerability. The vulnerability impacts availability significantly while having no effect on confidentiality or integrity.
The vulnerability affects all versions of the Linux kernel prior to the patch, specifically from versions 5.5 to 5.15.177, 5.16 to 6.1.127, 6.2 to 6.6.74, and 6.7 to 6.12.11. The affected products include various releases of the Linux kernel.
Technical Analysis
The root cause of CVE-2025-21666 lies in the Linux kernel's handling of vsock connections. The issue manifests when a vsock socket is called without proper checks after being de-assigned from its transport layer. This could lead to a null pointer dereference, resulting in a system crash or inconsistent states.
The attack vector for this vulnerability is local, meaning that an attacker must have local access to the system to exploit this flaw. The attack complexity is low, as it does not require specialized knowledge or advanced techniques to trigger the vulnerability. Privileges required to exploit this vulnerability are low, which increases the risk of exploitation.
User interaction is not required to exploit this vulnerability. The potential impact on availability is high, as it can lead to system crashes. However, there is no impact on confidentiality or integrity.
Risk & Impact Analysis
The risk to organizations includes potential service disruptions and impacts on system availability. Given the nature of the vulnerability, a successful exploit could lead to significant downtime, affecting business operations and service delivery. The urgency for addressing this vulnerability is underscored by its medium severity rating and the potential for high availability impact.
Organizations should assess their exposure to this vulnerability based on their deployment of the Linux kernel. The blast radius could be substantial, particularly in environments relying heavily on Linux for critical applications.
Given the CVSS score of 5.5, organizations should address this in their priority patch cycle. The presence of similar vulnerabilities in the future suggests that proactive measures should be taken to validate the integrity and availability of systems running the Linux kernel.
Exploitation Status
Signal | Status |
|---|---|
Known Exploit | No |
Public PoC | No |
Actively Exploited | No |
Ransomware Use | No |
Affected Versions
All versions of the Linux kernel prior to vendor patch are affected. This includes versions ranging from 5.5 to 5.15.177, 5.16 to 6.1.127, 6.2 to 6.6.74, and 6.7 to 6.12.11. Specific release candidates of version 6.13 are also vulnerable.
Mitigation & Remediation
To remediate this vulnerability, organizations should immediately apply the relevant patches provided by the Linux kernel maintainers. The patches can be found in the following links:
penetration testing to validate the effectiveness of the applied patches.
If patches are not immediately available, organizations should implement workarounds, such as restricting access to potentially vulnerable functionalities and closely monitoring logs for any unusual behavior.
Detection Guidance
To detect potential exploitation attempts, organizations should monitor log files for indicators of abnormal vsock behavior and unauthorized access attempts. Behavioral anomalies in the kernel logs should be closely scrutinized.
Network signatures that identify unusual traffic patterns involving vsock communications can also be valuable. Additionally, system changes that coincide with the detection of these anomalies should be investigated further.
AppSecure Threat Intelligence Insight
The long-term significance of CVE-2025-21666 highlights the need for robust validation mechanisms in the Linux kernel development process. This vulnerability serves as a reminder of the importance of thoroughly reviewing code changes that affect critical kernel functionalities.
It represents a pattern where oversight in socket management can lead to significant vulnerabilities. Security teams should take this as an opportunity to enhance their code review processes and implement more stringent testing protocols.
Overall, strategic defensive takeaways include the necessity of conducting regular audits and adopting a proactive approach to vulnerability management. Organizations can benefit from engaging in vulnerability management programs that ensure timely identification and remediation of vulnerabilities in critical systems.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
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