In the Linux kernel, a high-severity vulnerability has been identified. This vulnerability allows for potential memory corruption due to improper handling of control transfer buffer sizes in the usb: cdc-acm component. Organizations should prioritize patching immediately to mitigate risks associated with this flaw.
The CVSS score for this vulnerability is 7.8, indicating a high level of severity. Affected systems include multiple versions of the Linux kernel. The risk to organizations includes potential system instability and unauthorized access to sensitive data. Immediate remediation is strongly recommended.
As of now, there is no confirmed public exploit available for this vulnerability. However, organizations should not be complacent, as the potential for exploitation exists. The urgency of addressing this issue cannot be overstated.
Given the implications of this vulnerability, it is critical for organizations to schedule remediation as part of their security processes. Systems should be monitored closely for any signs of exploitation activities.
Vulnerability Details
In the Linux kernel, the following vulnerability has been resolved: usb: cdc-acm: Check control transfer buffer size before access. If the first fragment is shorter than struct usb_cdc_notification, we can't calculate an expected_size. Log an error and discard the notification instead of reading lengths from memory outside the received data, which can lead to memory corruption when the expected_size decreases between fragments, causing `expected_size - acm->nb_index` to wrap.
This issue has been present since the beginning of git history; however, it only leads to memory corruption since commit ea2583529cd1 ("cdc-acm: reassemble fragmented notifications"). A mitigating factor is that acm_ctrl_irq() can only execute after userspace has opened /dev/ttyACM*; but if ModemManager is running, ModemManager will do that automatically depending on the USB device's vendor/product IDs and its other interfaces.
The CVSS 3.1 vector string for this vulnerability is CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H, reflecting a local attack vector with low complexity and low privileges required. The impacts on confidentiality, integrity, and availability are all rated high.
Technical Analysis
The root cause of this vulnerability lies in the improper handling of control transfer buffer sizes. The attack vector is local, requiring access to the system where the Linux kernel operates. The attack complexity is low, and the privileges required are also low, allowing attackers with limited access to exploit this vulnerability.
User interaction is not required to exploit this vulnerability, which increases the risk profile. If exploited, the potential impacts include high confidentiality, integrity, and availability impacts.
Risk & Impact Analysis
Real-world deployment risk is significant given the high CVSS score of 7.8. Organizations relying on the Linux kernel for critical applications may face severe consequences if this vulnerability is exploited. Potential blast radius includes compromised systems that could lead to unauthorized access to sensitive data.
Organizations should address this vulnerability in their priority patch cycle. The urgency assessment based on CVSS indicates immediate action is required to ensure system integrity and confidentiality.
Exploitation Status
Signal | Status |
|---|---|
Known Exploit | No |
Public PoC | No |
Actively Exploited | No |
Ransomware Use | No |
Affected Versions
Affected versions of the Linux kernel include all versions prior to vendor patch, specifically those from 2.6.13 to 6.12.16, as well as various release candidates.
Mitigation & Remediation
Organizations should apply the latest patches from the Linux kernel to remediate this vulnerability. For guidance on effective patching strategies, consider our penetration testing services. Additionally, implementing configuration hardening and monitoring for suspicious activities is essential.
Detection Guidance
Monitoring logs for indicators of exploitation attempts and observing behavioral anomalies can help in early detection of any attempts to exploit this vulnerability. Network signatures and system changes should also be monitored closely.
AppSecure Threat Intelligence Insight
The long-term significance of this vulnerability lies in its potential to cause severe system instability and data loss. It represents a pattern of vulnerabilities that may arise from the complexity of kernel operations and the nature of hardware interactions.
Security teams should take lessons from this incident to prioritize rigorous testing of kernel interactions in future updates. For further insights on proactive measures, refer to our penetration testing methodology and consider implementing our vulnerability management program design for ongoing assessments.
In conclusion, organizations must remain vigilant and proactive in addressing vulnerabilities such as CVE-2025-21704 to safeguard their systems and data integrity.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
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