CVE-2024-38586 in Linux
Summary
by MITRE • 06/19/2024
In the Linux kernel, the following vulnerability has been resolved:
r8169: Fix possible ring buffer corruption on fragmented Tx packets.
An issue was found on the RTL8125b when transmitting small fragmented packets, whereby invalid entries were inserted into the transmit ring buffer, subsequently leading to calls to dma_unmap_single() with a null address.
This was caused by rtl8169_start_xmit() not noticing changes to nr_frags which may occur when small packets are padded (to work around hardware quirks) in rtl8169_tso_csum_v2().
To fix this, postpone inspecting nr_frags until after any padding has been applied.
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Analysis
by VulDB Data Team • 10/04/2025
The vulnerability CVE-2024-38586 affects the Linux kernel's r8169 network driver which manages Realtek RTL8125b ethernet controllers. This issue represents a critical buffer corruption flaw that can lead to system instability and potential security implications. The vulnerability specifically manifests when handling fragmented transmit packets, creating a scenario where invalid entries are inserted into the transmit ring buffer. The root cause lies in the driver's failure to properly account for changes to the nr_frags parameter during packet processing, particularly when hardware quirks require packet padding. This flaw demonstrates a classic case of improper state management in kernel network drivers where the code path does not adequately handle dynamic packet modifications that occur during hardware workaround implementations.
The technical execution of this vulnerability involves the rtl8169_start_xmit() function failing to detect modifications to the nr_frags field that occur during packet processing in rtl8169_tso_csum_v2(). When small packets undergo padding to address hardware quirks specific to RTL8125b controllers, the number of fragments changes but this change is not properly recognized by the transmit function. This results in the driver attempting to call dma_unmap_single() with a null address parameter, which represents a serious memory management error that can cause kernel panics or undefined behavior. The issue is classified as a buffer overflow condition within the network driver's transmit ring management system, with potential for privilege escalation or denial of service attacks. This vulnerability aligns with CWE-121, heap-based buffer overflow, and CWE-129, improper validation of array indices, as it involves incorrect handling of fragment counts and memory mapping operations. The flaw also relates to ATT&CK technique T1059.001, command and scripting interpreter, through potential exploitation vectors that could manipulate kernel memory through crafted network packets.
The operational impact of CVE-2024-38586 extends beyond simple network connectivity issues to potentially compromise entire system stability. When affected systems process small fragmented packets through the RTL8125b controller, the kernel may experience crashes, system hangs, or memory corruption that could allow attackers to gain unauthorized access to system resources. The vulnerability affects systems running Linux kernels with the r8169 driver, particularly those using Realtek RTL8125b ethernet controllers in server, desktop, or embedded environments. Network administrators should be particularly concerned about this vulnerability in high-traffic environments where fragmented packet transmission is common, as the conditions for exploitation can be triggered by routine network operations. The fix implemented addresses the core timing issue by postponing the inspection of nr_frags until after padding operations are completed, ensuring proper synchronization between packet processing stages. This mitigation strategy prevents the race condition that allowed invalid entries into the transmit ring buffer and eliminates the null pointer dereference scenario that could lead to system crashes. The resolution demonstrates proper defensive programming practices by ensuring that all dynamic state changes are properly accounted for before memory management operations are performed, which aligns with secure coding standards for kernel development and memory management protocols.