crypto/pcrypt.c in the Linux kernel before 4.14.13 mishandles freeing instances, allowing a local user able to access the AFALG-based AEAD interface (CONFIGCRYPTOUSERAPIAEAD) and pcrypt (CONFIGCRYPTO_PCRYPT) to cause a denial of service (kfree of an incorrect pointer) or possibly have unspecified other impact by executing a crafted sequence of system calls.