In the Linux kernel, a vulnerability has been identified and resolved regarding the RISC-V PMU driver. The issue arises from the failure to properly update the PERF_HES_STOPPED flag in the riscv_pmu_start() function when the perf_event_overflow() is called. This oversight can lead to performance degradation and a WARN_ON_ONCE() warning during operation.
The severity level of this vulnerability is classified as medium, with a CVSS score of 5.5. The attack vector is local, and while the complexity is low, the potential impact on system availability is high. Thus, the urgency for defenders to address this vulnerability is significant.
Organizations should prioritize patching immediately, as failure to do so could result in operational inefficiencies and system warnings that may disrupt normal processes.
The vulnerability was made public on October 4, 2025. It is essential for organizations running affected versions of the Linux kernel to remain vigilant and implement any necessary updates as soon as possible.
With no known exploits currently available for this vulnerability, organizations have a window of opportunity to remediate the issue before it becomes actively exploited.
Vulnerability Details
This vulnerability allows the RISC-V PMU driver to incorrectly handle performance events, which can result in system performance issues. Specifically, the absence of proper handling of the PERF_HES_STOPPED flag can lead to unnecessary warnings and the potential for throttled events.
The official CVE description highlights that since commit 096b52fd2bb4, the system's handling of performance events has changed. Consequently, if the interrupt duration exceeds certain limits, the performance framework is designed to throttle event reporting, which in turn can cause this vulnerability to manifest.
The vulnerability has been classified under CVSS 3.1 with a vector string of CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H, indicating a medium severity level that could severely impact availability without confidentiality or integrity concerns.
Technical Analysis
The root cause of this vulnerability lies in the RISC-V PMU driver's failure to update the PERF_HES_STOPPED flag correctly. This oversight occurs in the pmu_sbi_ovf_handler() function after the call to perf_event_overflow(). The design flaw allows the system to continue to trigger a WARN_ON_ONCE() warning when performance events are unthrottled.
The attack vector is local, requiring low privileges to exploit. There is no user interaction required for the vulnerability to manifest, which increases the risk profile for systems utilizing the affected kernel versions.
Although the integrity and confidentiality impacts are rated as none, the availability impact is rated as high. This indicates that systems could face operational issues, potentially disrupting services.
Risk & Impact Analysis
The real-world risk associated with this vulnerability includes potential service interruptions and degraded performance for applications relying on the Linux kernel. As the issue is tied to performance event handling, it could affect a wide range of applications running on systems with the affected kernel versions.
Organizations should assess the blast radius of this vulnerability, considering that it affects multiple versions of the Linux kernel. The urgency assessment based on the current CVSS score indicates that organizations should address this vulnerability in their priority patch cycle.
As this issue has not been marked as actively exploited in the KEV catalog, organizations have an opportunity to remediate the issue before it escalates into a larger threat.
Exploitation Status
Signal | Status |
|---|---|
Known Exploit | No |
Public PoC | No |
Actively Exploited | No |
Ransomware Use | No |
Affected Versions
This vulnerability affects all versions of the Linux kernel from 6.1 up to, but not including, 6.1.40, as well as versions from 6.2 to 6.4.5 and the 6.5-rc1 release.
Mitigation & Remediation
Organizations are advised to implement the latest patches released by the Linux kernel team to address this vulnerability. Affected users should upgrade to versions 6.1.40 or higher, 6.4.5 or higher, or 6.5 or later to mitigate the risk.
In cases where immediate patching is not feasible, consider implementing configuration hardening to limit the exposure to potential effects of this vulnerability.
Organizations may also benefit from continuous security testing practices to ensure the integrity and performance of their systems and to catch similar vulnerabilities in the future. Conducting a thorough security review can help identify other potential weaknesses.
For further assistance, organizations can explore our services on penetration testing to validate their security posture.
Detection Guidance
To detect any anomalies related to this vulnerability, organizations should monitor logs for performance event warnings and unexpected throttling behavior. Additionally, reviewing system performance metrics can help identify any unusual activity.
Behavioral anomalies in the performance metrics may indicate attempts to exploit this vulnerability. Regular audits of system performance and configuration can assist in identifying deviations from normal operations.
AppSecure Threat Intelligence Insight
This vulnerability highlights the importance of robust performance management in kernel development. The RISC-V PMU driver’s issues show a potential gap in handling performance events, which could be exploited in the future if left unaddressed.
Security teams should take this incident as a learning opportunity to improve their testing protocols for kernel performance management. Regular updates and thorough testing of kernel changes can help prevent similar vulnerabilities from being introduced.
For organizations looking to strengthen their security posture, reviewing our guide on penetration testing methodology can provide insights into best practices.
Additionally, organizations may benefit from understanding the trends in vulnerability management to stay ahead of potential risks.
Known Exploitation Timeline
As of now, this vulnerability has not been included in the KEV catalog, indicating that it is not currently being actively exploited.
Affected Versions
The affected versions of the Linux kernel include:
1. All versions from 6.1 up to but not including 6.1.40.2. All versions from 6.2 up to but not including 6.4.5.3. Version 6.5-rc1.
Mitigation & Remediation
Organizations should apply patches as soon as they are available. If immediate patching is not possible, configuration hardening and monitoring for unusual behavior may help mitigate risks.
For comprehensive security assessments, consider engaging in continuous penetration testing to validate your security controls.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
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