CVE-2026-43391 (GCVE-0-2026-43391)

Vulnerability from cvelistv5 – Published: 2026-05-08 14:21 – Updated: 2026-08-05 12:27
VLAI
Title
nsfs: tighten permission checks for handle opening
Summary
In the Linux kernel, the following vulnerability has been resolved: nsfs: tighten permission checks for handle opening 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: 5222470b2fbb3740f931f189db33dd1367b1ae75 , < 1797ee11451f1b2be69863a9f5bd43b948813fdf (git)
Affected: 5222470b2fbb3740f931f189db33dd1367b1ae75 , < d2324a9317f00013facb0ba00b00440e19d2af5e (git)
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Linux Linux Affected: 6.18
Unaffected: 0 , < 6.18 (semver)
Unaffected: 6.19.9 , ≤ 6.19.* (semver)
Unaffected: 7.0 , ≤ * (original_commit_for_fix)
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              "value": "AV:L - The vulnerable path is reached through the local open_by_handle_at(2) syscall using the nsfs root anchor, then handle_to_path() -\u003e exportfs_decode_fh_raw() -\u003e nsfs_fh_to_dentry(). It is not reachable via network packets or physical interaction.\nAC:L - There is no race or memory-layout dependency; once the attacker supplies a valid or discoverable nsfs handle/namespace id, the authorization bypass is deterministic. Namespace ids are exposed through nsfs/listing interfaces and are not cryptographic secrets.\nPR:L - The pre-fix check required CAP_SYS_ADMIN in the target namespace\u0027s owning user namespace, which can be satisfied by a user-namespace/container root in plausible deployments. This is privileged local access, but not necessarily real root in the initial namespace.\nUI:N - Exploitation is performed entirely by the attacking process via syscalls. No victim user action is required.\nS:C - The bug lets one namespace-confined privileged context obtain handles to another service\u0027s namespaces, crossing the namespace/sandbox visibility boundary that the fix restores. The impacted resources can be outside the attacker\u0027s intended namespace security domain.\nC:H - An unauthorized namespace fd exposes namespace metadata and can be used with setns paths to enter target mount, IPC, UTS, network, or related namespaces when the old capability gate is satisfied. In a severe deployment this can expose private service resources and secrets.\nI:H - After obtaining the namespace fd, the attacker can join target namespaces where existing capability checks allow it and modify namespace-scoped state such as mounts, IPC objects, hostnames, or service environment. This supports high integrity impact against the isolated service domain.\nA:H - The same unauthorized namespace access can be used to disrupt target namespace state, such as breaking mounts or other namespace-scoped resources needed by the victim service. In the highest reasonable scenario this can cause complete service availability loss."
            }
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-43391",
    "datePublished": "2026-05-08T14:21:36.012Z",
    "dateReserved": "2026-05-01T14:12:56.007Z",
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    "redhat_vex": {
      "aggregate_severity": "None",
      "current_release_date": "2026-06-28T07:37:18+00:00",
      "cve": "CVE-2026-43391",
      "id": "CVE-2026-43391",
      "initial_release_date": "2026-05-08T00:00:00+00:00",
      "product_status:known_not_affected": "274",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: nsfs: tighten permission checks for handle opening",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-43391.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.