crypto/pcrypt.c in the Linux kernel before 4.14.13 mishandles freeing instances, allowing a local user able to access the AF_ALG-based AEAD interface (CONFIG_CRYPTO_USER_API_AEAD) and pcrypt (CONFIG_CRYPTO_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.
https://www.kernel.org/pub/linux/kernel/v4.x/ChangeLog-4.14.13
https://usn.ubuntu.com/3619-2/
https://usn.ubuntu.com/3619-1/
https://github.com/torvalds/linux/commit/d76c68109f37cb85b243a1cf0f40313afd2bae68
https://access.redhat.com/errata/RHSA-2018:2948