x86: speculative vulnerability in 32bit SYSCALL path Due to an oversight in the very original Spectre/Meltdown security work (XSA-254), one entrypath performs its speculation-safety actions too late. In some configurations, there is an unprotected RET instruction which can be attacked with a variety of speculative attacks.
https://xenbits.xenproject.org/xsa/advisory-429.txt
https://www.debian.org/security/2023/dsa-5378
https://security.gentoo.org/glsa/202402-07