CVE-2026-68365 in Linux
Summary
by MITRE • 08/10/2026
In the Linux kernel, the following vulnerability has been resolved:
USB: serial: io_edgeport: cap received transmit credits
The interrupt-status packet reports transmit credits returned by the device. edge_interrupt_callback() adds the 16-bit value to txCredits without checking maxTxCredits.
edge_write() uses txCredits minus the software FIFO count as the amount of data that fits. Since the FIFO is allocated with maxTxCredits bytes, txCredits exceeding maxTxCredits can cause OOB write in ring buffer.
Cap accumulated credits at maxTxCredits. Conforming devices should never hit the cap.
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Analysis
by VulDB Data Team • 08/10/2026
The vulnerability resides within the Linux kernel's USB serial driver implementation, specifically in the io_edgeport module that handles communication with certain USB-to-serial adapters. This flaw represents a classic buffer overflow condition that could potentially be exploited to compromise system integrity. The issue manifests in the edge_interrupt_callback function which processes interrupt status packets from USB devices, where transmit credits returned by the hardware are directly added to the txCredits counter without proper bounds checking against the maximum allowed credits value.
The technical implementation flaw stems from a lack of input validation in the interrupt handling routine where the 16-bit credit value received from the device is blindly accumulated into the transmit credit counter. This design oversight creates a scenario where legitimate device behavior could cause the credit counter to exceed its allocated maximum capacity, leading to memory corruption within the kernel's ring buffer management system. The vulnerability specifically affects the edge_write function which calculates available space in the software FIFO by subtracting the current FIFO count from txCredits, assuming that txCredits never exceeds maxTxCredits.
When transmit credits accumulate beyond the maximum allowed threshold, the subsequent calculation in edge_write causes an out-of-bounds write operation within the ring buffer structure. This occurs because the software FIFO is allocated with a fixed size based on maxTxCredits bytes, but the code allows txCredits to grow beyond this boundary. The resulting memory corruption can lead to arbitrary code execution or system crashes depending on the specific memory locations overwritten during the out-of-bounds write operation.
This vulnerability aligns with CWE-129 Input Validation and Output Processing of External Input and CWE-787 Out-of-bounds Write categories, representing a classic case of insufficient boundary checking in kernel space operations. The attack surface is particularly concerning as it involves USB device communication which is frequently accessed by userspace applications and system services, potentially allowing for privilege escalation or denial of service conditions. From an adversarial perspective, this flaw fits within the ATT&CK technique T1068 Exploitation for Privilege Escalation, where kernel-level buffer overflows can be leveraged to gain elevated system privileges.
The recommended mitigation strategy involves implementing proper bounds checking in the edge_interrupt_callback function to cap accumulated transmit credits at maxTxCredits value as suggested in the fix. Additionally, system administrators should ensure all USB devices are running the latest firmware updates that may address device-side behavior causing excessive credit accumulation. Kernel-level security hardening measures such as kernel page table isolation and control flow integrity checks can provide additional defense-in-depth protection against exploitation attempts targeting this class of vulnerability. The fix demonstrates the importance of proper input validation in kernel space drivers where hardware communication protocols must be carefully validated against expected operational parameters to prevent memory corruption vulnerabilities.