The Linux kernel's pcrypt module installs a completion callback (pcrypt_aead_done()) on child AEAD requests before submitting them via padata. If padata_do_parallel() returns -EBUSY, indicating the parallel submission is busy, pcrypt falls back to calling the child AEAD request directly. Previously, this fallback path incorrectly retained the padata completion callback, leading to asynchronous completion invoking pcrypt_aead_done() even though the request was not enrolled in padata. The vulnerability is fixed by restoring the original request callback and callback data before invoking the child AEAD directly, ensuring the fallback path behaves consistently with direct AEAD requests and preventing unintended asynchronous callback execution.

The vulnerability could cause asynchronous completion callbacks to execute improperly when the fallback path is taken, potentially leading to unexpected behavior or instability in the crypto subsystem. No known exploits in the wild have been reported. The impact is limited to the internal handling of AEAD requests in the Linux kernel's crypto pcrypt module.

A fix has been applied to the Linux kernel to restore the original request callback and callback data in the fallback path of the pcrypt module. Users should update to a Linux kernel version that includes this fix. Patch status is not explicitly stated; check the vendor or Linux kernel advisories for the specific fixed versions and apply updates accordingly.