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The vulnerability resides in the `smscufx` framebuffer driver for SMSC UFX USB display devices. The core issue is in the handling of the `UFX_IOCTL_REPORT_DAMAGE` ioctl command. In the Linux kernel, data must be safely transferred between userspace and kernelspace using dedicated functions like `copy_from_user()` to prevent security issues. The vulnerable code directly dereferenced a userspace pointer (area = (struct dloarea )arg;) within the kernel context instead of copying the memory first. This means the kernel would attempt to read from a memory address controlled by a userspace program without proper validation. An attacker with local access and the ability to interact with the framebuffer device could pass invalid, malicious, or unmapped pointers. This could lead to a kernel crash (denial of service) due to an invalid memory access. In more severe scenarios, if the memory layout is favorable, this flaw could potentially be leveraged for information disclosure or privilege escalation, as the kernel might operate on attacker-controlled data directly. The fix, introduced by Greg Kroah-Hartman, replaces the direct pointer usage with a safe kernel allocation followed by a `copy_from_user()` operation, ensuring all user data is validated before use .
Platform: Linux Kernel
Version: Multiple versions
Vulnerability: Improper Ioctl Memory Copy
Severity: Medium
Date: March 4, 2026
Prediction: Patch by March 18, 2026
What Undercode Say:
Analysis:
The vulnerability is a classic case of failing to use `copy_from_user` in an ioctl handler. The patch adds a kernel memory allocation and the necessary copy operation .
Patch Code Snippet (from `drivers/video/fbdev/smscufx.c`) :
static int ufx_ops_ioctl(struct fb_info info, unsigned int cmd,
unsigned long arg)
{
struct ufx_data dev = info->par;
- struct dloarea area = NULL;
/ ... /
if (cmd == UFX_IOCTL_REPORT_DAMAGE) {
+ struct dloarea area __free(kfree) = kmalloc(sizeof(area), GFP_KERNEL);
+ if (!area)
+ return -ENOMEM;
+
/ ... /
- area = (struct dloarea )arg;
+ if (copy_from_user(area, (u8 __user )arg, sizeof(area)))
+ return -EFAULT;
Bash Commands for Detection and Mitigation :
Check if the smscufx module is currently loaded lsmod | grep smscufx Temporarily unload the vulnerable module (mitigation) sudo modprobe -r smscufx Permanently blacklist the module to prevent loading on boot echo "blacklist smscufx" | sudo tee /etc/modprobe.d/smscufx-blacklist.conf sudo update-initramfs -u Restrict permissions on framebuffer devices (use with caution) sudo chmod 600 /dev/fb
How Exploit:
Vector: Local
Prerequisites: Attacker must have local access to a system with the `smscufx` driver loaded and be able to open the framebuffer device node (e.g., /dev/fb).
Method: The attacker crafts a malicious ioctl call with the `UFX_IOCTL_REPORT_DAMAGE` command. Instead of a valid pointer to a `dloarea` structure, they pass an invalid or specially crafted kernel address. When the vulnerable driver dereferences this address directly, it causes a kernel panic or potentially corrupts kernel memory .
Protection from this CVE:
- Apply Patch: Update the Linux kernel to a version that includes the commit by Greg Kroah-Hartman, which adds the `copy_from_user` check .
- Module Blacklisting: If the SMSC UFX hardware is not required, blacklist the `smscufx` kernel module to prevent it from loading .
- Restrict Device Access: Use filesystem permissions or Mandatory Access Control (SELinux/AppArmor) to limit which users and processes can open framebuffer device files .
Impact:
Availability: High. The most direct and likely impact is a kernel oops or panic, leading to a system crash and denial of service .
Confidentiality & Integrity: Potential. While not proven publicly, improper handling of user pointers can sometimes be exploited for privilege escalation or information disclosure under specific conditions .
Scope: Affects systems with the `CONFIG_FB_SMSCUFX` kernel build flag enabled, which includes many generic and LTS kernels as shown in Ubuntu’s CVE tracking . The EPSS score predicts a low (0.03%) probability of exploitation in the wild within 30 days .
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Sources:
Reported By: nvd.nist.gov
Extra Source Hub:
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