CVE-2021-47561·Kernel vulnerability
In the Linux kernel, the following vulnerability has been resolved: i2c: virtio: disable timeout handling If a timeout is hit, it can result is incorrect data on the I2C bus and/or memory corruptions in the guest since the device can still be operating on the buffers it was given while the guest has freed them. Here is, for example, the start of a slub_debug splat which was triggered on the next transfer after one transfer was forced to timeout by setting a breakpoint in the backend (rust-vmm/vhost-device): BUG kmalloc-1k (Not tainted): Poison overwritten First byte 0x1 instead of 0x6b Allocated in virtio_i2c_xfer+0x65/0x35c age=350 cpu=0 pid=29 __kmalloc+0xc2/0x1c9 virtio_i2c_xfer+0x65/0x35c __i2c_transfer+0x429/0x57d i2c_transfer+0x115/0x134 i2cdev_ioctl_rdwr+0x16a/0x1de i2cdev_ioctl+0x247/0x2ed vfs_ioctl+0x21/0x30 sys_ioctl+0xb18/0xb41 Freed in virtio_i2c_xfer+0x32e/0x35c age=244 cpu=0 pid=29 kfree+0x1bd/0x1cc virtio_i2c_xfer+0x32e/0x35c __i2c_transfer+0x429/0x57d i2c_transfer+0x115/0x134 i2cdev_ioctl_rdwr+0x16a/0x1de i2cdev_ioctl+0x247/0x2ed vfs_ioctl+0x21/0x30 sys_ioctl+0xb18/0xb41 There is no simple fix for this (the driver would have to always create bounce buffers and hold on to them until the device eventually returns the buffers), so just disable the timeout support for now.
- Severity
- high
- Software
- Kernel
- Fixed in
- 5.15.6
- Published
- 2024-05-24
Affected versions
From: 5.15
Until: 5.15.6
Fixed in: 5.15.6
How to fix this CVE
Update your Linux kernel to version 5.15.6 or later to resolve this virtualized I2C timeout handling vulnerability. The virtio-i2c driver's timeout mechanism could allow the device to operate on freed memory buffers, leading to data corruption and kernel memory issues. Apply the patch immediately if you are running affected kernel versions 5.15.0 through 5.15.5.
sudo dnf update kernel kernel-develDefensia detects this vulnerability
How to check if you are affected
- Step 1: Check your current kernel version with: uname -r (should be 5.15.6 or later to be patched)
- Step 2: Verify if virtio-i2c driver is loaded: lsmod | grep virtio_i2c (if empty, component is not in use)
- Step 3: Search kernel logs for I2C timeout errors and slub_debug poisoning messages: sudo dmesg | grep -i 'i2c.*timeout\|poison overwritten'
- Step 4: After patching, reboot the system and confirm new kernel version: sudo reboot && uname -r
FAQ
What is CVE-2021-47561?
CVE-2021-47561 is a critical vulnerability in the Linux kernel's virtio-i2c driver where timeout handling can cause the hypervisor to access memory buffers that the guest OS has already freed, resulting in memory corruption and data integrity issues on virtualized I2C buses.
Is CVE-2021-47561 being actively exploited?
No, this vulnerability is not listed in CISA's Known Exploited Vulnerabilities (KEV) catalog and no public exploits are currently available. However, the high CVSS score of 7.8 reflects its serious impact on system stability.
What versions of Kernel are affected by CVE-2021-47561?
Linux kernel versions 5.15.0 through 5.15.5 are vulnerable. Version 5.15.6 and later contain the fix that disables the problematic timeout handling in the virtio-i2c driver.
How do I check if my server is vulnerable to CVE-2021-47561?
Run 'uname -r' to check your kernel version; if it shows 5.15.0 through 5.15.5, you are vulnerable. Additionally, verify the virtio-i2c driver is in use with 'lsmod | grep virtio_i2c'.
Does Defensia detect CVE-2021-47561?
Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If Kernel is installed on a monitored server, CVE-2021-47561 will appear in your dashboard with remediation steps.
Related Kernel CVEs
References
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