CVE-2021-4002: Medium severity Linux Linux kernel vulnerability
A memory leak flaw in the Linux kernel's hugetlbfs memory usage was found in the way the user maps some regions of memory twice using shmget() which are aligned to PUD alignment with the fault of some of the memory pages. A local user could use this flaw to get unauthorized access to some data.
Other sources
On Linux 3.6 and later is is possible to leak or corrupt data that resides on hugetlbs. Such data can reside on hugetlbfs, for instance, if the victim runs mmap() using the MAPHUGETLB or shmget() with SHMHUGETLB.
The bug is caused due to a missing TLB flush when unmapping of a page of PMDs is performed by clearing a PUD. While the comment in the code claims that it is safe, it is not since no flush would take place under these circumstances (unless, of course it was needed for some other reason).
— Red Hat
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
redhat/kernel-rtto a version that resolves this vulnerability.Fixed in 0:4.18.0-372.9.1.rt7.166.el8 - Upgrade
Upgrade
redhat/kernelto a version that resolves this vulnerability.Fixed in 0:4.18.0-372.9.1.el8 - Upgrade
Upgrade
redhat/kernelto a version that resolves this vulnerability.Fixed in 5.16 - Upgrade
Upgrade
debian/linuxto a version that resolves this vulnerability.Fixed in 6.1.176-1Fixed in 6.1.190-1Fixed in 6.12.107-1Fixed in 6.12.115-2Fixed in 7.2.15-1
Event History
Parent advisories
This vulnerability appears in the following advisories.
Frequently Asked Questions
What is the severity of CVE-2021-4002?
The severity of CVE-2021-4002 is categorized as medium.
How do I fix CVE-2021-4002?
To fix CVE-2021-4002, update the Linux kernel to version 0:4.18.0-372.9.1.rt7.166.el8 or 0:4.18.0-372.9.1.el8 or any appropriate version that addresses the vulnerability.
Who is affected by CVE-2021-4002?
CVE-2021-4002 affects local users on systems running vulnerable versions of the Linux kernel where hugetlbfs is utilized.
What is the nature of CVE-2021-4002?
CVE-2021-4002 is a memory leak vulnerability in the Linux kernel's hugetlbfs memory usage.
Can CVE-2021-4002 lead to unauthorized access?
Yes, CVE-2021-4002 could allow a local user to gain unauthorized access to sensitive data.