CVE-2021-47218: linux kernel Null Dereference — Fix

Description

In the Linux kernel, the following vulnerability has been resolved: selinux: fix NULL-pointer dereference when hashtab allocation fails When the hash table slot array allocation fails in hashtab_init(), h->size is left initialized with a non-zero value, but the h->htable pointer is NULL. This may then cause a NULL pointer dereference, since the policydb code relies on the assumption that even after a failed hashtab_init(), hashtab_map() and hashtab_destroy() can be safely called on it. Yet, these detect an empty hashtab only by looking at the size. Fix this by making sure that hashtab_init() always leaves behind a valid empty hashtab when the allocation fails.

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CVSS v3.1 Score

5.5

MEDIUM

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Weakness Type (CWE)

CWE-476 CWE-476

Affected Products

Vendor	Product	Versions
linux	linux_kernel	5.8 — 5.10.82
linux	linux_kernel	5.11 — 5.15.5
linux	linux_kernel	All
linux	linux_kernel	All

References

Advisories & Patches

https://git.kernel.org/stable/c/83c8ab8503adf56bf68dafc7a382f4946c87da79 https://git.kernel.org/stable/c/b17dd53cac769dd13031b0ca34f90cc65e523fab https://git.kernel.org/stable/c/dc27f3c5d10c58069672215787a96b4fae01818b https://git.kernel.org/stable/c/83c8ab8503adf56bf68dafc7a382f4946c87da79 https://git.kernel.org/stable/c/b17dd53cac769dd13031b0ca34f90cc65e523fab https://git.kernel.org/stable/c/dc27f3c5d10c58069672215787a96b4fae01818b

Frequently Asked Questions

What is CVE-2021-47218? +

In the Linux kernel, the following vulnerability has been resolved: selinux: fix NULL-pointer dereference when hashtab allocation fails When the hash table slot array allocation fails in hashtab_init(), h->size is left initialized with a non-zero value, but the h->htable pointer is NULL. This may then cause a NULL pointer dereference, since the policydb code relies on the assumption that even after a failed hashtab_init(), hashtab_map() and hashtab_destroy() can be safely called on it. Yet, these detect an empty hashtab only by looking at the size. Fix this by making sure that hashtab_init() always leaves behind a valid empty hashtab when the allocation fails. It has a CVSS v3.1 base score of 5.5 (MEDIUM).

How severe is CVE-2021-47218? +

CVE-2021-47218 has a CVSS v3.1 score of 5.5 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance.

What products are affected by CVE-2021-47218? +

CVE-2021-47218 affects products from linux, specifically: linux_kernel. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2021-47218? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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CVE-2021-47218