CVE-2024-56638 netfilter: nft_inner: incorrect percpu area handling under softirq
A race condition in Linux kernel netfilter allows softirqs to corrupt percpu data, potentially causing system crashes or instability.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2024-56638?
CVE-2024-56638 is a high-severity vulnerability in Linux kernel, published on 27 Dec 2024. It can only be exploited from the same machine or local network, with no action from the victim.
Official 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.
Which versions are affected by CVE-2024-56638?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2024-56638?
Apply the vendor's patch.
Is CVE-2024-56638 being exploited?
There is no known exploitation of CVE-2024-56638 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2024-56638, DEBIAN-CVE-2024-56638, GHSA-7g3g-qg84-qxww, UBUNTU-CVE-2024-56638.