Kernel-memory disclosure via unchecked HID report length
Published Sep 11, 2026 · Updated Sep 11, 2026
Out-of-bounds read in Linux allows physically proximate attackers to disclose kernel memory through a crafted USB HID report. In mcp2221_raw_event(), the MCP2221_I2C_GET_DATA path uses device-controlled data[3] as a memcpy length without confirming that the received report contains 4 + data[3] bytes. Exploitation requires an attached malicious or misbehaving MCP2221 device, and the exposed bytes reach userspace through an I2C or SMBus read.
Summary
What happened
Out-of-bounds read in Linux allows physically proximate attackers to disclose kernel memory through a crafted USB HID report. In mcp2221_raw_event(), the MCP2221_I2C_GET_DATA path uses device-controlled data[3] as a memcpy length without confirming that the received report contains 4 + data[3] bytes. Exploitation requires an attached malicious or misbehaving MCP2221 device, and the exposed bytes reach userspace through an I2C or SMBus read.
The record
- CVE
- CVE-2026-89621
- Published
- Sep 11, 2026
- Updated
- Sep 11, 2026
- Vendor
- The Linux Kernel Organization
- Product
- Linux
- Classifications
- T1200
- Attack vector
- physical
- Privileges
- unauthenticated
Timeline
How it unfolded
- Sep 11, 2026CVE publishedPublication date reported by the CVE source.
- Sep 11, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
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- Affected versionversion=5.7
- Affected versionversion=67a95c21463d066060b0f66d65a75d45bb386ffb <127de5919820f88a9d55e8371ad4ac49f625f4c5
- Affected versionversion=67a95c21463d066060b0f66d65a75d45bb386ffb <2c9a6998c19503626c57a2267bf279e204113079
- Affected versionversion=67a95c21463d066060b0f66d65a75d45bb386ffb <7c18fb36708a97ff6772825cc087b6d537bbf0d5
- Affected versionversion=67a95c21463d066060b0f66d65a75d45bb386ffb <bdc6a3af0dd734a326acdb7d6401a3b6a9f4f149
What conditions does exploitation require?
What is affected?
Published CVSS scores
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Attacks
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Weakness, pattern, technique
Public exploit references
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Technologies
Your stack
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Your stack
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