CVE-2026-63902

In the Linux kernel, the following vulnerability has been resolved:

USB: serial: cypress_m8: validate interrupt packet headers

cypress_read_int_callback() parses the interrupt-in buffer according to the selected Cypress packet format. Format 1 has a two-byte status/count header and format 2 has a one-byte combined status/count header. The usb-serial core sizes the interrupt-in buffer from the endpoint descriptors wMaxPacketSize, and successful interrupt transfers can complete short when URB_SHORT_NOT_OK is not set.

Check that the completed packet contains the selected header before reading it. Malformed short reports are ignored and the interrupt URB is resubmitted through the existing retry path, preventing out-of-bounds header-byte reads.

KASAN report as below: KASAN slab-out-of-bounds in cypress_read_int_callback+0x240/0x7f0 Read of size 1 Call trace: cypress_read_int_callback() (drivers/usb/serial/cypress_m8.c:1009) __usb_hcd_giveback_urb() dummy_timer()

[ johan: use constants in header length sanity checks ]

Weakness

The product reads data past the end, or before the beginning, of the intended buffer.

Affected Software

Potential Mitigations

• Assume all input is malicious. Use an “accept known good” input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
• When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, “boat” may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as “red” or “blue.”
• Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code’s environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
• To reduce the likelihood of introducing an out-of-bounds read, ensure that you validate and ensure correct calculations for any length argument, buffer size calculation, or offset. Be especially careful of relying on a sentinel (i.e. special character such as NUL) in untrusted inputs.

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/540.html

References

• https://git.kernel.org/stable/c/44f9bab8df7750a1e2a4d6cc22d7c9c2dc096aed
• https://git.kernel.org/stable/c/4a4cb0021ebe1fcadb52e04d19ed8d71470a530b
• https://git.kernel.org/stable/c/90664556916de22467097d4c8ceb716d597a5c32
• https://git.kernel.org/stable/c/9f9bfc80c67f35a275820da7e83a35dface08281
• https://git.kernel.org/stable/c/aaa66708bfb1dca2acd219d1c1582f9f6d5492cb
• https://git.kernel.org/stable/c/ae03453f2c809ca3cf73753269fa6184dea7160f
• https://git.kernel.org/stable/c/be50533fe7068e86eb7adb81988e6d6a3f6dfe53
• https://git.kernel.org/stable/c/fcef31a5a85ccf3c313449a866ec6ed7e4132425