UBUNTU-CVE-2026-63903: Medium severity ubuntu/linux vulnerability
In the Linux kernel, the following vulnerability has been resolved: USB: serial: belkinsa: validate interrupt status length The Belkin interrupt callback treats interrupt data as a four-byte status report and reads LSR/MSR fields at offsets 2 and 3. The interrupt-in buffer length is derived from endpoint wMaxPacketSize, and short interrupt transfers may complete successfully with a smaller actuallength. Check the completed interrupt packet length before parsing status fields so short interrupt endpoints and short successful packets are ignored instead of causing out-of-bounds or stale status-byte reads. KASAN report as below: BUG: KASAN: slab-out-of-bounds in belkinsareadintcallback() Read of size 1 Call trace: belkinsareadintcallback() (drivers/usb/serial/belkinsa.c:202) usbhcdgivebackurb() (drivers/usb/core/hcd.c:1630) dummytimer() (?:?)
Affected Software
Remediation
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ubuntu/linux-riscvto a version that resolves this vulnerability.Fixed in 7.0.0-28.28.1 - Compensating control
In the Linux kernel USB serial Belkin driver, validate the completed interrupt packet actual_length before parsing status fields; ignore short interrupt endpoints and short successful packets unless the buffer contains the four-byte status report, preventing reads of LSR/MSR at offsets 2 and 3.
Event History
Frequently Asked Questions
Which Ubuntu kernel package variants are affected?
The advisory applies to Ubuntu linux, linux-fips, linux-aws, linux-azure, linux-aws-fips, linux-azure-fips, linux-gcp, and linux-gcp-fips packages.
What conditions are required to trigger the issue?
The vulnerable path is the Belkin USB serial driver interrupt callback. A short successful interrupt transfer, or an interrupt endpoint with a packet size shorter than the expected four-byte status report, can cause the driver to read status fields beyond the completed data.
What is the impact of a malformed or short interrupt packet?
The driver can perform out-of-bounds reads or consume stale status bytes while parsing the line-status and modem-status fields. The reported failure is a KASAN slab-out-of-bounds read in belkin_sa_read_int_callback().
What does the fix change?
The fix validates the completed interrupt packet length before parsing status fields. Packets that are too short are ignored rather than being interpreted as four-byte status reports.