CVE-2019-12822 is a vulnerability that affects the Linux kernel, particularly versions 2.6.29 and above. It is caused by a flaw in the implementation of the "runlatch" mechanism, which is used to synchronize access to memory pages mapped as read-only. The vulnerability allows an attacker to gain write access to those memory pages, which can result in a variety of attacks such as privilege escalation, denial of service, and information leakage.
The vulnerability was first reported on July 11, 2019, and was assigned CVE-2019-12822 on July 12, 2019. Various Linux distributions released patches for the vulnerability shortly after its disclosure. However, because the vulnerability had been present in the Linux kernel for over a decade, it is possible that many systems remain vulnerable. To exploit the vulnerability, an attacker would need to have local access to the system or be able to execute arbitrary code on the system.
In summary, CVE-2019-12822 is a serious vulnerability in the Linux kernel that could allow an attacker to gain write access to read-only memory pages, resulting in various types of attacks. While patches have been released for the vulnerability, it is possible that many systems remain vulnerable due to the long history of the flaw. System administrators are advised to ensure that their systems are updated with the latest security patches to mitigate the risk of attacks exploiting this vulnerability.