macsec: don't read an unset MAC header in macsec_encrypt()

These records connect through source-stated identifiers. Shared identifiers or dates alone do not establish shared exposure, root cause or applicability.

CVE-2026-72019 · Microsoft / collected KEV context

cve-program · CVE-2026-72019

• https://git.kernel.org/stable/c/b6cec6187b8632423cd99a94fd5e5ba165fa2a33
• https://git.kernel.org/stable/c/3adea1b1c04b57e08a5c12a1f42483760581ce61
• https://git.kernel.org/stable/c/dc9ffa1905e72f026d080880a2e4cfc42aa91000
• https://git.kernel.org/stable/c/f21fa533a3ed15ada74106aac4b9ddd078fc6b7a
• https://git.kernel.org/stable/c/e17a42199824973cd8212e95b21ffadf4114a21b
• https://git.kernel.org/stable/c/2cf10d042562283ff4ae97c02d0993d4f1b5ea29
• https://git.kernel.org/stable/c/c39087ad0b97fc11a3b058dfc8db9fd370762cb9
• https://git.kernel.org/stable/c/f5089008f90c0a7c5520dff3934e0af00adf322d

No related operational record is retained in the current change model.