CVE-2026-43183 Overview
CVE-2026-43183 is a resource leak vulnerability in the Linux kernel's cx25821 media driver. The flaw resides in the cx25821_dev_setup() function, which fails to release a previously reserved memory region when the subsequent ioremap() call fails. The memory region acquired through cx25821_get_resources() remains allocated, leading to a kernel resource leak on the error path. The upstream fix adds a release_mem_region() call to properly unwind the partial initialization state when ioremap() returns an error.
Critical Impact
Repeated triggering of the failure path can exhaust kernel-managed I/O memory regions, contributing to denial-of-service conditions on systems using the cx25821 PCI media capture hardware.
Affected Products
- Linux kernel media subsystem (drivers/media/pci/cx25821)
- Systems with Conexant CX25821-based video capture cards
- Multiple stable kernel branches addressed by the listed patch commits
Discovery Timeline
- 2026-05-06 - CVE-2026-43183 published to NVD
- 2026-05-06 - Last updated in NVD database
Technical Details for CVE-2026-43183
Vulnerability Analysis
The cx25821 driver supports Conexant CX25821-based PCI video capture devices. During device probing, cx25821_dev_setup() calls cx25821_get_resources() to reserve the device's memory-mapped I/O region using request_mem_region(). The driver then calls ioremap() to map that region into the kernel virtual address space.
The defect occurs on the error path. If ioremap() returns NULL, the function exits without invoking release_mem_region(). The reserved memory region remains marked as in use within the kernel's resource tree, even though no driver instance owns it.
This leak persists for the lifetime of the running kernel. Each unsuccessful probe attempt against the affected hardware path consumes additional resource tracking entries.
Root Cause
The root cause is incomplete error-path cleanup, a class of defect related to memory leak [CWE-401] semantics in resource management. The function paired the acquisition (cx25821_get_resources()) with the mapping (ioremap()) but did not symmetrically release the acquisition when the mapping failed.
Attack Vector
Triggering the leak requires the ioremap() call to fail during driver initialization. This typically occurs under low kernel virtual address space conditions or hardware enumeration anomalies. A local attacker with the ability to repeatedly bind and unbind the driver, or to induce probe failures on affected hardware, can amplify the leak. Remote exploitation is not applicable because the code path requires local PCI driver interaction. No public exploit is associated with this CVE.
No verified exploitation code is published. Refer to the upstream fix commits for the precise patch logic.
Detection Methods for CVE-2026-43183
Indicators of Compromise
- Kernel log entries indicating ioremap() failures referencing the cx25821 driver during PCI device probing.
- Growing /proc/iomem entries associated with the cx25821 BAR region without an active driver binding.
- Increasing slab and resource tree consumption following repeated driver load or unload cycles on affected hardware.
Detection Strategies
- Monitor dmesg and persistent kernel logs for cx25821 probe errors paired with ioremap failure messages.
- Inventory running kernel versions across the fleet and compare against the patched stable branches referenced in the kernel commits.
- Audit systems with Conexant CX25821 PCI capture hardware to confirm the loaded driver originates from a patched build.
Monitoring Recommendations
- Track kernel resource usage metrics on long-running hosts that perform frequent driver rebinding for media hardware.
- Alert on repeated cx25821_dev_setup failures, which indicate the leak path is being exercised.
- Centralize kernel logs in a SIEM or data lake to correlate driver errors with system stability events.
How to Mitigate CVE-2026-43183
Immediate Actions Required
- Update affected systems to a Linux kernel build that includes the upstream fix commits listed in the references.
- Restrict physical and administrative access to systems hosting cx25821 capture cards to limit local probe manipulation.
- If the cx25821 hardware is not in use, blacklist the kernel module to remove exposure to the vulnerable code path.
Patch Information
The fix adds a release_mem_region() call on the ioremap() failure path inside cx25821_dev_setup(). The patch is distributed across multiple stable kernel branches in commits 071bfc6, 4010e5c, 68cd8ac, 80ce379, 9f1c926, b721017, e220ec4, and f7759eb. Apply the kernel update appropriate to your distribution's supported branch.
Workarounds
- Blacklist the cx25821 module on systems that do not require Conexant CX25821 capture functionality.
- Disable automatic driver binding for the affected PCI device IDs through udev rules until a patched kernel is deployed.
- Avoid repeated rebind or hot-plug cycles for cx25821 hardware on unpatched systems to reduce leak amplification.
# Blacklist the cx25821 module until a patched kernel is installed
echo "blacklist cx25821" | sudo tee /etc/modprobe.d/blacklist-cx25821.conf
sudo update-initramfs -u
# Verify the module is not loaded after reboot
lsmod | grep cx25821
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
