CVE-2025-38420: Linux Kernel WiFi Driver Vulnerability Leads to Potential Null Pointer Dereference

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CVE-2025-38420: Linux Kernel WiFi Driver Vulnerability Leads to Potential Null Pointer Dereference

This blog post discusses a recently identified vulnerability, CVE-2025-38420, affecting the Linux kernel's carl9170 WiFi driver. This flaw can lead to a null pointer dereference if the WiFi device fails to load its firmware, potentially causing a system crash.

🔍 TL;DR Summary

A vulnerability in the Linux kernel's carl9170 WiFi driver can cause a null pointer dereference if the device fails to load its firmware. This can lead to a system crash. A patch has been released to address this issue.

🚨 Vulnerability Details

  • CVE ID: CVE-2025-38420
  • Description: The carl9170 WiFi driver attempts to ping a device that has failed to load its firmware. Because the device hasn't completed the registration process (ieee80211_register_hw()), the necessary internal workqueue isn't initialized. Attempting to queue work to this non-existent workqueue results in a null pointer dereference.
  • CVSS Score and Vector: Currently awaiting analysis. Based on similar kernel vulnerabilities, a score in the Medium range (4.0 - 6.0) is likely, potentially leading to Denial of Service (DoS). The vector would likely involve local exploitation since it relates to device initialization.
  • Exploit Requirements: The device must fail to load its firmware. This could be due to hardware issues, corrupted firmware, or other initialization errors.
  • Affected Vendor, Product, Version: Linux kernel (specific versions affected depend on the patch backporting). Affected kernels likely include versions containing the vulnerable carl9170 driver code.
  • CWE: CWE-476 - Null Pointer Dereference. This occurs when the program attempts to access memory through a pointer that has a null value. This leads to a crash or unpredictable behavior.

📅 Timeline of Events

  • Reported: Unknown (likely through internal testing or fuzzing)
  • Discovered By: Syzkaller (fuzzing tool)
  • Patched: A patch has been implemented to prevent pinging the device before the workqueue is initialized.
  • Published (CVE): 2025-07-25

🧠 Exploitability & Real-World Risk

The exploitability of this vulnerability is dependent on the circumstances that cause the firmware loading to fail. While not directly remotely exploitable, if an attacker can induce a firmware loading failure (e.g., by tampering with the firmware image if stored insecurely), they could trigger the null pointer dereference and cause a denial-of-service. The real-world risk is moderate, as it requires specific hardware and software conditions to be met.

🛠️ Recommendations

  • Apply the Patch: Update to the latest kernel version or apply the appropriate patch for your kernel version. Check your distribution's security advisories for updates.
  • Monitor System Logs: Keep an eye on system logs for any errors related to firmware loading or the carl9170 driver.
  • Secure Firmware Storage: Ensure the integrity of the WiFi firmware image by storing it securely and using checksum verification.

🧪 Technical Insight

The core issue lies in the timing of the device initialization. The carl9170 driver attempts to communicate with the WiFi device even when the device hasn't fully initialized due to a failed firmware load. The missing workqueue, which is necessary for asynchronous operations, leads to a null pointer dereference when the driver tries to use it. The fix ensures the driver only attempts to communicate with the device after the workqueue has been successfully initialized.

🙌 Credit to Researcher(s)

Discovered by Syzkaller (fuzzing tool).

🔗 References

🧵 Tags

#Linux #Kernel #WiFi #carl9170 #CVE-2025-38420 #NullPointerDereference #SecurityVulnerability

Summary: A vulnerability exists in the Linux kernel's carl9170 WiFi driver where an attempt to ping a device that failed to load its firmware can cause a null pointer dereference, leading to a potential system crash. Update to the latest kernel version or apply the provided patch to mitigate this issue.

CVE ID: CVE-2025-38420

Risk Analysis: A successful exploit can lead to a denial-of-service condition, causing the system to crash. This can disrupt services relying on the affected system.

Recommendation: Update to the latest kernel version or apply the appropriate patch for your kernel version. Monitor system logs for any errors related to firmware loading or the carl9170 driver.

Timeline

  • 2025-07-25: CVE-2025-38420 Published

References

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