CVE-2017-17806 on Ubuntu 18.04 LTS (bionic) - medium.
Description:
The HMAC implementation (crypto/hmac.c) in the Linux kernel before 4.14.8 does not validate that the underlying cryptographic hash algorithm is unkeyed, allowing a local attacker able to use the AF_ALG-based hash interface (CONFIG_CRYPTO_USER_API_HASH) and the SHA-3 hash algorithm (CONFIG_CRYPTO_SHA3) to cause a kernel stack buffer overflow by executing a crafted sequence of system calls that encounter a missing SHA-3 initialization. It was discovered that the HMAC implementation did not validate the state of the underlying cryptographic hash algorithm. A local attacker could use this to cause a denial of service (system crash) or possibly execute arbitrary code.