CVE-2026-99201 (GCVE-0-2026-99201)

Vulnerability from cvelistv5 – Published: 2026-10-28 10:35 – Updated: 2026-10-30 12:42
VLAI
Title
netlink: avoid hashing the network namespace pointer
Summary
In the Linux kernel, the following vulnerability has been resolved: netlink: avoid hashing the network namespace pointer The netlink rhashtable key includes a raw struct net pointer and a user-controlled port ID. Both /proc/net/netlink and socket diagnostics expose the table's bucket order. By binding and rebinding chosen NETLINK_USERSOCK port IDs, an unprivileged reader can distinguish equal buckets and recover the low bits of the Jenkins hash. Its 32-bit seed and the limited set of kernel-image slides can then be searched offline to recover the address of init_net. Use the namespace's unique, non-address net_cookie in the comparison key instead. It is assigned before the per-net initializers run and remains unchanged for the namespace's lifetime. The lookup key and object hash are still built by netlink_compare_arg_init(), keeping lookup, insertion, removal and rehashing consistent while preserving namespace separation. Neither public table walker needs to change. Reading the socket's namespace cookie in netlink_compare() is safe under RCU, including during namespace teardown. netlink_release() removes the socket from the hash table and defers its final put with call_rcu(). cleanup_net() runs the per-net exit methods and waits for outstanding RCU callbacks with rcu_barrier() before freeing namespace storage. Unlike ns.ns_id, net_cookie is also available and initialized during setup_net() in older stable kernels, making the change straightforward to backport to v5.15 and later.
Severity
No CVSS data available.
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 6649 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: c428ecd1a21f1457ca3beb4df71b8a079c410e41 , < c61431f3b8c9824e9848a0308054f92b27fa7794 (git)
Affected: c428ecd1a21f1457ca3beb4df71b8a079c410e41 , < f8d2690f3c5dfad1fc306f6d5d84a1d3176c3af9 (git)
Affected: c428ecd1a21f1457ca3beb4df71b8a079c410e41 , < c03fb9c4be3b2dd0996d91e54f65407f7f475238 (git)
Affected: c428ecd1a21f1457ca3beb4df71b8a079c410e41 , < 41a2f69f091b0765f17890d8ac04852c12f25cf6 (git)
Affected: c428ecd1a21f1457ca3beb4df71b8a079c410e41 , < 18edcb9945118beb7a1b64a31a7370ecab485a79 (git)
Affected: c428ecd1a21f1457ca3beb4df71b8a079c410e41 , < bdd55b8a8acbf6b4840ab420eb6a63774bf4593b (git)
Affected: c428ecd1a21f1457ca3beb4df71b8a079c410e41 , < 078deff25f8a849ecd1c3fe17b1e473b1cf44f28 (git)
Affected: c428ecd1a21f1457ca3beb4df71b8a079c410e41 , < f88bb3606e4bd11ee035b682cddc2999e604609a (git)
guessed Create a notification for this product.
Linux Linux Affected: 4.1
Unaffected: 0 , < 4.1 (semver)
Unaffected: 5.10.273 , ≤ 5.10.* (semver)
Unaffected: 5.15.224 , ≤ 5.15.* (semver)
Unaffected: 6.1.191 , ≤ 6.1.* (semver)
Unaffected: 6.6.161 , ≤ 6.6.* (semver)
Unaffected: 6.12.115 , ≤ 6.12.* (semver)
Unaffected: 6.18.59 , ≤ 6.18.* (semver)
Unaffected: 7.2.13 , ≤ 7.2.* (semver)
Unaffected: 7.3 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnetlink: avoid hashing the network namespace pointer\n\nThe netlink rhashtable key includes a raw struct net pointer and a\nuser-controlled port ID. Both /proc/net/netlink and socket diagnostics\nexpose the table\u0027s bucket order. By binding and rebinding chosen\nNETLINK_USERSOCK port IDs, an unprivileged reader can distinguish equal\nbuckets and recover the low bits of the Jenkins hash. Its 32-bit seed\nand the limited set of kernel-image slides can then be searched offline\nto recover the address of init_net.\n\nUse the namespace\u0027s unique, non-address net_cookie in the comparison\nkey instead. It is assigned before the per-net initializers run and\nremains unchanged for the namespace\u0027s lifetime. The lookup key and\nobject hash are still built by netlink_compare_arg_init(), keeping\nlookup, insertion, removal and rehashing consistent while preserving\nnamespace separation. Neither public table walker needs to change.\n\nReading the socket\u0027s namespace cookie in netlink_compare() is safe\nunder RCU, including during namespace teardown. netlink_release()\nremoves the socket from the hash table and defers its final put with\ncall_rcu(). cleanup_net() runs the per-net exit methods and waits for\noutstanding RCU callbacks with rcu_barrier() before freeing namespace\nstorage.\n\nUnlike ns.ns_id, net_cookie is also available and initialized during\nsetup_net() in older stable kernels, making the change straightforward\nto backport to v5.15 and later."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-30T12:42:51.128Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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        },
        {
          "url": "https://git.kernel.org/stable/c/f88bb3606e4bd11ee035b682cddc2999e604609a"
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      ],
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    "cveId": "CVE-2026-99201",
    "datePublished": "2026-10-28T10:35:56.069Z",
    "dateReserved": "2026-09-25T10:25:14.400Z",
    "dateUpdated": "2026-10-30T12:42:51.128Z",
    "state": "PUBLISHED"
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      "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-99201.json",
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        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnetlink: avoid hashing the network namespace pointer\n\nThe netlink rhashtable key includes a raw struct net pointer and a\nuser-controlled port ID. Both /proc/net/netlink and socket diagnostics\nexpose the table\u0027s bucket order. By binding and rebinding chosen\nNETLINK_USERSOCK port IDs, an unprivileged reader can distinguish equal\nbuckets and recover the low bits of the Jenkins hash. Its 32-bit seed\nand the limited set of kernel-image slides can then be searched offline\nto recover the address of init_net.\n\nUse the namespace\u0027s unique, non-address net_cookie in the comparison\nkey instead. It is assigned before the per-net initializers run and\nremains unchanged for the namespace\u0027s lifetime. The lookup key and\nobject hash are still built by netlink_compare_arg_init(), keeping\nlookup, insertion, removal and rehashing consistent while preserving\nnamespace separation. Neither public table walker needs to change.\n\nReading the socket\u0027s namespace cookie in netlink_compare() is safe\nunder RCU, including during namespace teardown. netlink_release()\nremoves the socket from the hash table and defers its final put with\ncall_rcu(). cleanup_net() runs the per-net exit methods and waits for\noutstanding RCU callbacks with rcu_barrier() before freeing namespace\nstorage.\n\nUnlike ns.ns_id, net_cookie is also available and initialized during\nsetup_net() in older stable kernels, making the change straightforward\nto backport to v5.15 and later."
          }
        ],
        "id": "CVE-2026-99201",
        "lastModified": "2026-10-30T13:21:52.503",
        "metrics": {},
        "published": "2026-10-28T11:17:41.250",
        "references": [
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          },
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            "url": "https://git.kernel.org/stable/c/c03fb9c4be3b2dd0996d91e54f65407f7f475238"
          },
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            "url": "https://git.kernel.org/stable/c/c61431f3b8c9824e9848a0308054f92b27fa7794"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/f88bb3606e4bd11ee035b682cddc2999e604609a"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/f8d2690f3c5dfad1fc306f6d5d84a1d3176c3af9"
          }
        ],
        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Received"
      }
    },
    "redhat_vex": {
      "aggregate_severity": "Low",
      "current_release_date": "2026-11-02T14:34:48+00:00",
      "cve": "CVE-2026-99201",
      "id": "CVE-2026-99201",
      "initial_release_date": "2026-10-28T10:35:56.069000+00:00",
      "product_status:known_affected": "280",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: kernel: Information disclosure via netlink network namespace pointer hashing",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-99201.json",
      "version": "3"
    }
  }
}



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  • 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.
Vulnerability timeline

Sightings and recorded dates, grouped by day · UTC

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How durations are calculated

Following the VTEM framework (Black Hat USA 2015), time to patch starts when the vendor or a coordinator was informed, total time to patch at discovery, and disclosure to patch at public disclosure; vendor response time runs from the report to its acknowledgement. Time to exploit and time unpatched start at the earliest discovery or report, falling back to public disclosure. Unpatched time ends at the first recorded patch, or the calculation time when no patch is recorded. Exploitation to patch shows the interval between those two events; a published proof of concept is a public exploit, not exploitation.

Each result shows its source dates. A negative interval means the end event came first; when date-only inputs leave the order open, the result says so. Date-only inputs are approximate. The earliest evidence wins: KEV report dates and sightings are labelled as such. Records describing another vulnerability are listed but never calculated from, and a PoC alone does not establish exploitation. Missing patch evidence does not prove that no patch exists. Filters below change the event list only.

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