# CVE-2026-43042: mpls: add seqcount to protect the platform_label{,s} pair

CVE-2026-43042 is fixed in linux on 1 platform, first by DEBIAN-CVE-2026-43042, released May 15, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-43042
- Priority: High
- CVSS: 7.1 (Important)
- EPSS: 0.0013
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: May 1, 2026
- Weakness: Out-of-bounds Read
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-43042

## 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 13.5 (trixie) | 6.12.115-2 | [DEBIAN-CVE-2026-43042](https://patchblox.com/security/data/fix/linux/debian-cve-2026-43042.md) | May 15, 2026 |
| Linux | linux Debian 14 | 6.19.12-1 | [DEBIAN-CVE-2026-43042](https://patchblox.com/security/data/fix/linux/debian-cve-2026-43042.md) | May 15, 2026 |

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Data as of 2026-11-09T01:18:40Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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