CVE-2024-56638: linux kernel — Fix

Description

In the Linux kernel, the following vulnerability has been resolved: netfilter: nft_inner: incorrect percpu area handling under softirq Softirq can interrupt ongoing packet from process context that is walking over the percpu area that contains inner header offsets. Disable bh and perform three checks before restoring the percpu inner header offsets to validate that the percpu area is valid for this skbuff: 1) If the NFT_PKTINFO_INNER_FULL flag is set on, then this skbuff has already been parsed before for inner header fetching to register. 2) Validate that the percpu area refers to this skbuff using the skbuff pointer as a cookie. If there is a cookie mismatch, then this skbuff needs to be parsed again. 3) Finally, validate if the percpu area refers to this tunnel type. Only after these three checks the percpu area is restored to a on-stack copy and bh is enabled again. After inner header fetching, the on-stack copy is stored back to the percpu area.

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CVSS v3.1 Score

7.8

HIGH

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

Affected Products

Vendor	Product	Versions
linux	linux_kernel	6.2 — 6.6.66
linux	linux_kernel	6.7 — 6.12.5
linux	linux_kernel	All

References

Advisories & Patches

https://git.kernel.org/stable/c/53c7314208c865086d78b4e88da53bc33da0b603 https://git.kernel.org/stable/c/7b1d83da254be3bf054965c8f3b1ad976f460ae5 https://git.kernel.org/stable/c/da5cc778e7bf78fe525bc90ec2043f41415c31d9

Frequently Asked Questions

What is CVE-2024-56638? +

In the Linux kernel, the following vulnerability has been resolved: netfilter: nft_inner: incorrect percpu area handling under softirq Softirq can interrupt ongoing packet from process context that is walking over the percpu area that contains inner header offsets. Disable bh and perform three checks before restoring the percpu inner header offsets to validate that the percpu area is valid for this skbuff: 1) If the NFT_PKTINFO_INNER_FULL flag is set on, then this skbuff has already been parsed before for inner header fetching to register. 2) Validate that the percpu area refers to this skbuff using the skbuff pointer as a cookie. If there is a cookie mismatch, then this skbuff needs to be parsed again. 3) Finally, validate if the percpu area refers to this tunnel type. Only after these three checks the percpu area is restored to a on-stack copy and bh is enabled again. After inner header fetching, the on-stack copy is stored back to the percpu area. It has a CVSS v3.1 base score of 7.8 (HIGH).

How severe is CVE-2024-56638? +

CVE-2024-56638 has a CVSS v3.1 score of 7.8 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching.

What products are affected by CVE-2024-56638? +

CVE-2024-56638 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-2024-56638? +

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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