CVE-2026-43042 mpls: add seqcount to protect the platform_label{,s} pair
A race condition in the Linux kernel MPLS subsystem allows out-of-bounds memory access, potentially leading to code execution or denial of service.
- 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-2026-43042?
CVE-2026-43042 is a high-severity vulnerability in Linux kernel, published on 1 May 2026. 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:
mpls: add seqcount to protect the platform_label{,s} pair
The RCU-protected codepaths (mpls_forward, mpls_dump_routes) can have an inconsistent view of platform_labels vs platform_label in case of a concurrent resize (resize_platform_label_table, under platform_mutex). This can lead to OOB accesses.
This patch adds a seqcount, so that we get a consistent snapshot.
Note that mpls_label_ok is also susceptible to this, so the check against RTA_DST in rtm_to_route_config, done outside platform_mutex, is not sufficient. This value gets passed to mpls_label_ok once more in both mpls_route_add and mpls_route_del, so there is no issue, but that additional check must not be removed.
Which versions are affected by CVE-2026-43042?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-43042?
Apply the vendor's patch.
Is CVE-2026-43042 being exploited?
There is no known exploitation of CVE-2026-43042 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-85377, BELL-CVE-2026-43042, DEBIAN-CVE-2026-43042, GHSA-j45g-66j9-q94m, ROOT-OS-DEBIAN-11-CVE-2026-43042, ROOT-OS-DEBIAN-12-CVE-2026-43042 and 4 more.