CVE-2021-22555

Name of the Vulnerable Software and Affected Versions Linux versions prior to 2.6.19-rc1 are not specified, but versions since v2.6.19-rc1 are affected.

Description The issue is related to a heap out-of-bounds write in the netfilter subsystem of the Linux kernel, specifically in the net/netfilter/x tables.c file. This allows an attacker to gain privileges or cause a denial of service through user name space by exploiting the vulnerability in the xt compat target from user() function. The vulnerability can be exploited by calling compat setsockopt() with IPT SO SET REPLACE or IP6T SO SET REPLACE values set. A proof of concept exploit has been developed, which can bypass security mechanisms such as KASLR, SMAP, and SMEP, and achieve kernel code execution. The researcher who discovered the vulnerability received a $20,000 reward from Google for identifying a method to bypass container isolation in a Kubernetes cluster.

Recommendations As a temporary workaround, consider disabling the xt compat target from user() function until a patch is available. Restrict access to the netfilter subsystem to minimize the risk of exploitation. Avoid using the compat setsockopt() function with IPT SO SET REPLACE or IP6T SO SET REPLACE values set until the issue is resolved. At the moment, there is no information about a newer version that contains a fix for this vulnerability.