CVE-2026-31720
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USB Control Request Size Validation Flaw in Linux Kernel

Publication date: 2026-05-01

Last updated on: 2026-05-06

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: usb: gadget: f_uac1_legacy: validate control request size f_audio_complete() copies req->length bytes into a 4-byte stack variable: u32 data = 0; memcpy(&data, req->buf, req->length); req->length is derived from the host-controlled USB request path, which can lead to a stack out-of-bounds write. Validate req->actual against the expected payload size for the supported control selectors and decode only the expected amount of data. This avoids copying a host-influenced length into a fixed-size stack object.
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Meta Information
Published
2026-05-01
Last Modified
2026-05-06
Generated
2026-06-16
AI Q&A
2026-05-01
EPSS Evaluated
2026-06-15
NVD
CVE-2026-31720
EUVD
EUVD-2026-26533
Affected Vendors & Products
Showing 13 associated CPEs
Vendor Product Version / Range
linux linux_kernel 7.0
linux linux_kernel 7.0
linux linux_kernel 7.0
linux linux_kernel 7.0
linux linux_kernel 7.0
linux linux_kernel 7.0
linux linux_kernel From 5.11 (inc) to 5.15.203 (exc)
linux linux_kernel From 6.13 (inc) to 6.18.22 (exc)
linux linux_kernel From 5.16 (inc) to 6.1.168 (exc)
linux linux_kernel From 6.19 (inc) to 6.19.12 (exc)
linux linux_kernel From 6.7 (inc) to 6.12.81 (exc)
linux linux_kernel From 6.2 (inc) to 6.6.134 (exc)
linux linux_kernel From 2.6.31 (inc) to 5.10.253 (exc)
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-787 The product writes data past the end, or before the beginning, of the intended buffer.
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Mitigation Strategies

To mitigate this vulnerability, ensure that your Linux kernel is updated to a version where the issue has been resolved.

The vulnerability involves improper validation of USB control request sizes in the f_uac1_legacy driver, which has been fixed by validating the actual request size against the expected payload size.

Therefore, applying the latest kernel patches or updates that include this fix is the immediate step to prevent exploitation.

Executive Summary

This vulnerability exists in the Linux kernel's USB gadget function f_uac1_legacy, specifically in the f_audio_complete() function. The function copies a number of bytes specified by req->length into a fixed 4-byte stack variable without proper validation. Since req->length is controlled by the host through a USB request, this can lead to a stack out-of-bounds write, potentially causing memory corruption.

The fix involves validating the actual length of the request against the expected payload size for supported control selectors, ensuring only the expected amount of data is copied. This prevents copying a host-influenced length into a fixed-size stack object.

Impact Analysis

This vulnerability can lead to a stack out-of-bounds write, which may cause memory corruption. Such memory corruption can potentially be exploited to crash the system, execute arbitrary code, or escalate privileges, depending on the context and exploitability.

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