CVE-2026-64439

In the Linux kernel, the following vulnerability has been resolved:

crypto: krb5 - filter out async aead implementations at alloc

krb5aeadencrypt(), krb5aeaddecrypt() in rfc3961_simplified.c and

rfc8009encrypt(), rfc8009decrypt() in rfc8009_aes2.c set a NULL

completion callback and treat any negative return from

cryptoaead{encrypt,decrypt}() as terminal, falling through to

kfreesensitive(buffer).  When the encryptname resolves to an

async AEAD instance the request returns -EINPROGRESS, the buffer

is freed while the backend's worker still holds a pointer, and the

worker dereferences the freed slab on completion.

KASAN report under UML+SLUB with a synthetic async aead backend

bound to krb5->encrypt_name:

  BUG: KASAN: slab-use-after-free in t5stubcomplete+0x7d/0xc7

The helpers were written synchronously, so filter the async

instances out at allocation time instead of plumbing

cryptowaitreq() through every call site.

Reachable via net/rxrpc/rxgk.c, fs/afs/cm_security.c and

net/ceph/crypto.c on systems with an async AEAD provider bound to

the krb5 enctype name.