An issue was discovered in drivers/accessibility/speakup/spk_ttyio.c in the Linux kernel through 5.9.9. Local attackers on systems with the speakup driver could cause a local denial of service attack, aka CID-d41227544427. This occurs because of an invalid free when the line discipline is used more than once.
https://www.openwall.com/lists/oss-security/2020/11/19/3
https://lists.debian.org/debian-lts-announce/2020/12/msg00015.html
https://github.com/torvalds/linux/commit/d4122754442799187d5d537a9c039a49a67e57f1