UBUNTU-CVE-2026-98698: Medium severity ubuntu/linux-azure vulnerability

In the Linux kernel, the following vulnerability has been resolved: wifi: mac80211: handle empty FILS association request payload filsencryptassocreq() accepts a (Re)Association Request frame whose last element is the FILS Session element. cryptlen is then zero and aessivencrypt() is called with an empty plaintext. kmemdup() returns ZEROSIZEPTR for a zero-length allocation, so the unconditional sginitone() puts an invalid page into the scatterlist. With CONFIGDEBUGSG this triggers a kernel BUG in sgsetbuf(); without the debug check the bogus page is handed to the crypto backend. AES-SIV is defined for empty plaintext and the S2V result is then the complete output, so handle this case before the CTR step, which has nothing to encrypt.