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CVE-2026-89621: HID: mcp2221: validate report size in mcp2221_raw_event()

• Severity: unknown
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-09-11 · updated 2026-10-19

Description

In the Linux kernel, the following vulnerability has been resolved: HID: mcp2221: validate report size in mcp2221_raw_event() mcp2221_raw_event() never validates the size of incoming HID reports. In the MCP2221_I2C_GET_DATA path it trusts the device-supplied data[3] as the copy length without checking that 4 + data[3] bytes actually exist in the received report. A malicious or misbehaving USB device can send a short report with a large data[3], causing the memcpy to read past the valid report data in the HID transfer buffer and leak uninitialized kernel memory back to userspace through the I2C/SMBus read path. Add a minimum size check at entry and validate that the source range fits within the received report before the copy.

Affected products

• Linux kernel: 5.7 — fixed in 7.3

How to fix

Upgrade to a fixed version: Linux kernel 7.3. Check the vendor advisory for mitigations.

References

• https://git.kernel.org/stable/c/127de5919820f88a9d55e8371ad4ac49f625f4c5
• https://git.kernel.org/stable/c/2c9a6998c19503626c57a2267bf279e204113079
• https://git.kernel.org/stable/c/7c18fb36708a97ff6772825cc087b6d537bbf0d5
• https://git.kernel.org/stable/c/b2c67dc0e30c308647bbd9b9e5d69a44c9d2733d
• https://git.kernel.org/stable/c/bdc6a3af0dd734a326acdb7d6401a3b6a9f4f149
• https://git.kernel.org/stable/c/c1c508e8923911cb458234997e55b7a4b9aa066f
• https://git.kernel.org/stable/c/cb38b1f149b7143355b37e86c841acf0076e5c2a
• https://git.kernel.org/stable/c/fffcfa367072628c3144cca17d2a3c3c9e50c057

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