CVE-2026-43042 (GCVE-0-2026-43042)

Vulnerability from cvelistv5 – Published: 2026-05-01 14:15 – Updated: 2026-08-05 12:25
VLAI
Title
mpls: add seqcount to protect the platform_label{,s} pair
Summary
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.
Severity
7.1 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 7720c01f3f590116882e251f13c7e1d5602f8643 , < 5bb3caf0bbfb56f1a00d2af072ac3d8395a3b9ef (git)
Affected: 7720c01f3f590116882e251f13c7e1d5602f8643 , < 629ec78ef8608d955ce217880cdc3e1873af3a15 (git)
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Linux Linux Affected: 4.1
Unaffected: 0 , < 4.1 (semver)
Unaffected: 6.19.12 , ≤ 6.19.* (semver)
Unaffected: 7.0 , ≤ * (original_commit_for_fix)
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            "include/net/netns/mpls.h",
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              "value": "AV:L - The self-contained exploit path is local: the attacker races writes to /proc/sys/net/mpls/platform_labels with rtnetlink RTM_GETROUTE dumps in the same network namespace. Remote MPLS packets can reach one reader path, but a remote-only attacker cannot perform the required table resize.\nAC:L - The vulnerable condition is a race, but a local attacker can control both sides by repeatedly resizing platform_labels and issuing concurrent route dumps or packet processing. No external timing or victim state is required beyond retrying the race.\nPR:L - Writing the MPLS platform_labels sysctl requires CAP_NET_ADMIN over the target network namespace. That capability is reachable by an unprivileged user through a user namespace plus network namespace, so this is low privilege rather than high privilege.\nUI:N - No victim user action is required. The attacker can trigger the resize and reader paths directly.\nS:U - The bug is within the kernel networking/MPLS subsystem and impacts the same kernel security authority. It is not a VM escape or cross-authority boundary bypass.\nC:H - The inconsistent platform_labels/platform_label snapshot can cause out-of-bounds reads of the route pointer table and dereference attacker-influenced or adjacent kernel memory as mpls_route data. Through the route dump path this can disclose kernel memory, so confidentiality is high.\nI:N - The bug is an out-of-bounds read/dereference of the route table pointer array, not an out-of-bounds write or direct memory corruption primitive. The investigated paths do not provide a defensible arbitrary kernel data modification primitive.\nA:H - The race can make readers index a NULL, stale, or too-small platform_label array and dereference invalid pointers. This can reliably lead to kernel oops/panic or other high availability impact."
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}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


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