CVE-2026-43403 (GCVE-0-2026-43403)

Vulnerability from cvelistv5 – Published: 2026-05-08 14:21 – Updated: 2026-08-05 12:27
VLAI
Title
nsfs: tighten permission checks for ns iteration ioctls
Summary
In the Linux kernel, the following vulnerability has been resolved: nsfs: tighten permission checks for ns iteration ioctls Even privileged services should not necessarily be able to see other privileged service's namespaces so they can't leak information to each other. Use may_see_all_namespaces() helper that centralizes this policy until the nstree adapts.
Severity
8.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: a1d220d9dafa8d76ba60a784a1016c3134e6a1e8 , < 3376b345df155ca36d8611857b41ff7d5183fc38 (git)
Affected: a1d220d9dafa8d76ba60a784a1016c3134e6a1e8 , < 2f3dea284c761c890d676f77d5e55c0c496b4ef4 (git)
Affected: a1d220d9dafa8d76ba60a784a1016c3134e6a1e8 , < 0ad650e60150eda789deca5e78a6a09d26bf8fc9 (git)
Affected: a1d220d9dafa8d76ba60a784a1016c3134e6a1e8 , < e6b899f08066e744f89df16ceb782e06868bd148 (git)
guessed Create a notification for this product.
Linux Linux Affected: 6.12
Unaffected: 0 , < 6.12 (semver)
Unaffected: 6.12.78 , ≤ 6.12.* (semver)
Unaffected: 6.18.20 , ≤ 6.18.* (semver)
Unaffected: 6.19.9 , ≤ 6.19.* (semver)
Unaffected: 7.0 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
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{
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            "fs/nsfs.c",
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              "value": "AV:L - The vulnerable path is reached by a local `ioctl()` on an nsfs mount-namespace file descriptor, such as one obtained from `/proc/self/ns/mnt` or pidfd namespace ioctls. There is no network, adjacent, or physical attack path.\nAC:L - Triggering is deterministic: open a mount namespace fd and issue `NS_MNT_GET_NEXT` or `NS_MNT_GET_PREV`. There is no race or special memory-layout condition required.\nPR:L - The pre-fix check only required `CAP_SYS_ADMIN` in the target mount namespace\u0027s owning user namespace, which can be satisfied through user namespaces in plausible deployments. Under the higher-severity rule, this is Low rather than High.\nUI:N - No victim interaction is needed once the attacker has local execution and the relevant namespace capability. The attacker directly invokes the ioctl.\nS:C - The bug lets one namespace-confined service obtain file descriptors for other mount namespaces, bypassing the intended namespace visibility boundary. That can cross container or service isolation boundaries.\nC:H - The returned namespace fd and mount namespace id allow enumeration with `listmount()` and `statmount()`, exposing mount topology, paths, sources, options, and related metadata from another namespace. In plausible privileged-container scenarios, the fd can also enable `setns()` into the target mount namespace and expose sensitive filesystem contents.\nI:H - With the leaked mount namespace fd and the same namespace capabilities required by the vulnerable path, an attacker can plausibly `setns()` into another mount namespace and modify writable files or mount state there. This can compromise integrity across the namespace boundary.\nA:H - After obtaining and entering another mount namespace in a privileged scenario, the attacker can disrupt that namespace by altering or unmounting resources or damaging writable files. This can cause high availability impact to the affected service or container."
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    "datePublished": "2026-05-08T14:21:44.204Z",
    "dateReserved": "2026-05-01T14:12:56.007Z",
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    "state": "PUBLISHED"
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    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-07-02T12:46:46+00:00",
      "cve": "CVE-2026-43403",
      "id": "CVE-2026-43403",
      "initial_release_date": "2026-05-08T00:00:00+00:00",
      "product_status:known_affected": "76",
      "product_status:known_not_affected": "198",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: nsfs: tighten permission checks for ns iteration ioctls",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-43403.json",
      "version": "3"
    }
  }
}



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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.

Sightings

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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.


Detection rules are retrieved from Rulezet.