CVE-2024-41035: USB: core: Fix duplicate endpoint bug by clearing reserved bits in the descriptor
In the Linux kernel, the following vulnerability has been resolved:
USB: core: Fix duplicate endpoint bug by clearing reserved bits in the descriptor
Syzbot has identified a bug in usbcore (see the Closes: tag below)
caused by our assumption that the reserved bits in an endpoint
descriptor's bEndpointAddress field will always be 0. As a result of
the bug, the endpoint_is_duplicate() routine in config.c (and possibly
other routines as well) may believe that two descriptors are for
distinct endpoints, even though they have the same direction and
endpoint number. This can lead to confusion, including the bug
identified by syzbot (two descriptors with matching endpoint numbers
and directions, where one was interrupt and the other was bulk).
To fix the bug, we will clear the reserved bits in bEndpointAddress
when we parse the descriptor. (Note that both the USB-2.0 and USB-3.1
specs say these bits are "Reserved, reset to zero".) This requires us
to make a copy of the descriptor earlier in usb_parse_endpoint() and
use the copy instead of the original when checking for duplicates.
Security readout for executives and security teams
Plain-English summary
CVE-2024-41035 is a Linux kernel USB handling flaw. A malformed USB endpoint descriptor can make the kernel treat duplicate endpoints as different, creating internal confusion. The public record does not provide CVSS, confirmed impact, or active exploitation evidence.
Executive priority
Handle through normal kernel patch management, with higher priority where untrusted USB devices are common. There is no provided evidence of active exploitation, but kernel USB parsing bugs can matter operationally because they sit below application controls.
Technical view
Linux usbcore assumed reserved bits in bEndpointAddress were zero. When they were not cleared during parsing, endpoint_is_duplicate() could miss duplicate endpoint number and direction pairs. The resolved fix clears reserved bits while parsing copied endpoint descriptors.
Likely exposure
Exposure is most relevant to Linux systems that accept untrusted USB devices or USB passthrough into kernels using affected Linux versions. The source bundle lists Linux as affected and points to stable kernel fixes, but exact distro package exposure requires vendor mapping.
Exploitation context
The bundle cites syzbot discovery and kernel stable fixes. It does not cite KEV listing, public exploitation, exploit availability, or a complete impact statement. Treat active exploitation as not evidenced by the provided sources.
Researcher notes
Focus review on usb_parse_endpoint(), endpoint descriptor copying, bEndpointAddress reserved-bit masking, and duplicate endpoint detection. The source evidence supports malformed descriptor confusion, not broader impacts beyond what the kernel fix text describes.
Mitigation direction
Update to a Linux kernel containing the referenced stable usbcore fixes.
Use distribution security updates where available, including Debian LTS guidance if applicable.
Restrict physical or virtual USB device attachment on sensitive Linux systems.
Review vendor advisories for exact fixed package versions.
Avoid direct wrangler or deployment actions unrelated to kernel remediation.
Validation and detection
Inventory Linux kernel versions on systems that can receive USB devices.
Map running kernels to vendor advisories or the referenced stable commits.
Confirm distro packages include the usbcore reserved-bit clearing fix.
Review USB passthrough exposure in virtualization and appliance environments.
Prioritize systems with public kiosks, labs, or unmanaged peripheral access.
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Potential ATT&CK relevance
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