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CVE-2026-63995: ethtool: cmis: validate start_cmd_payload_size from module

• Severity: high (CVSS 7.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.1% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-07-19 · updated 2026-10-19
• Weakness: CWE-787

Description

In the Linux kernel, the following vulnerability has been resolved: ethtool: cmis: validate start_cmd_payload_size from module The CMIS firmware update code reads start_cmd_payload_size from the module's FW Management Features CDB reply and uses it directly as the byte count for memcpy. The destination buffer is 112 bytes (ETHTOOL_CMIS_CDB_LPL_MAX_PL_LENGTH - 8). So a malicious module (or corrupted response) can cause a OOB write later on in cmis_fw_update_start_download(). Let's error out. If modules that expect longer LPL writes actually exist we should revisit. struct cmis_cdb_start_fw_download_pl's definition has to move, no change there.

Affected products

• Linux kernel: from 6.11 before 6.12.93; from 6.13 before 6.18.35; from 6.19 before 7.0.12; 7.1-rc1, 7.1-rc2, 7.1-rc3, 7.1-rc4, 7.1-rc5 — fixed in 6.12.93, 6.18.35, 7.0.12

How to fix

Upgrade to a fixed version: Linux kernel 6.12.93, 6.18.35, 7.0.12. Check the vendor advisory for mitigations.

References

• https://git.kernel.org/stable/c/0696709e951be54c699664adf546d16e28974d53
• https://git.kernel.org/stable/c/12c2496a71f82f63617971ca9b730dffa05cf58b
• https://git.kernel.org/stable/c/63112b4515469d00008452d9cfe3fb3bf1aa2df3
• https://git.kernel.org/stable/c/a46340da00385be7fb16c62425ebc20006f2d5d8

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