CVE-2026-98870 (GCVE-0-2026-98870)

Vulnerability from cvelistv5 – Published: 2026-10-23 11:37 – Updated: 2026-10-24 14:09
VLAI
Title
ksmbd: remove stale channels from all sessions on teardown
Summary
In the Linux kernel, the following vulnerability has been resolved: ksmbd: remove stale channels from all sessions on teardown ksmbd_sessions_deregister() removes a connection's channels from other sessions' channel lists only while conn->binding is still set: if (conn->binding) { hash_for_each_safe(sessions_table, ...) ksmbd_chann_del(conn, sess); } conn->binding is a transient flag: it is cleared once a binding SESSION_SETUP completes, and also by a subsequent non-binding SESSION_SETUP on the same connection (a reauthentication on a bound channel, or a new SessionId==0 setup). A connection that has bound a channel into another session's ksmbd_chann_list and then clears conn->binding leaves that channel behind when it disconnects: the channel, whose chann->conn points at the now freed struct ksmbd_conn, stays on the owner session's list. When the owning connection later tears down, the second loop dereferences the stale channel: xa_for_each(&sess->ksmbd_chann_list, chann_id, chann) if (chann->conn != conn) ksmbd_conn_set_exiting(chann->conn); /* freed */ which is a use-after-free write into the freed ksmbd_conn (the same stale channel is also walked by show_proc_session() through /proc). The session is leaked as well, because its channel list never empties. Remove the conn->binding gate so a connection always removes its channels from every session on teardown.
Severity
8.8 (High)
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 6641 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: b1b6ed903a6e2b3505a48706bcd499b447ef9e44 , < f8200bb4994e65a2e5c5b314789eeae39078619d (git)
Affected: 47b018dba6ec7ebf403fd2d1e713bc7acc9bbb23 , < 9cd6d714d3ca0cff296542dc989696884e41970f (git)
Affected: 9ef4dfd5edbd02f4bf10cd420a30896093d98a67 , < b145f9b56c87f9c23ad5464ab0844dbc1de12b36 (git)
Affected: 5a5b0b7a01fe19b383b3c046546b5ae30c1a7d71 , < a15cae16f4432a5ad919ee633e31b07178492955 (git)
Affected: faf8578c77f3d846aca9cd882c293e03eafcc6df , < b10665730fbf6b5e45fe422badcbbc3f0df96ef5 (git)
Affected: e632f21a8bc0c59abc4960482836ac3782db93c0 (git)
Affected: 5.15.222 , < 5.16 (semver)
guessed Create a notification for this product.
Linux Linux guessed Create a notification for this product.
Show details on NVD website
To clipboard 

{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/smb/server/mgmt/user_session.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "f8200bb4994e65a2e5c5b314789eeae39078619d",
              "status": "affected",
              "version": "b1b6ed903a6e2b3505a48706bcd499b447ef9e44",
              "versionType": "git"
            },
            {
              "lessThan": "9cd6d714d3ca0cff296542dc989696884e41970f",
              "status": "affected",
              "version": "47b018dba6ec7ebf403fd2d1e713bc7acc9bbb23",
              "versionType": "git"
            },
            {
              "lessThan": "b145f9b56c87f9c23ad5464ab0844dbc1de12b36",
              "status": "affected",
              "version": "9ef4dfd5edbd02f4bf10cd420a30896093d98a67",
              "versionType": "git"
            },
            {
              "lessThan": "a15cae16f4432a5ad919ee633e31b07178492955",
              "status": "affected",
              "version": "5a5b0b7a01fe19b383b3c046546b5ae30c1a7d71",
              "versionType": "git"
            },
            {
              "lessThan": "b10665730fbf6b5e45fe422badcbbc3f0df96ef5",
              "status": "affected",
              "version": "faf8578c77f3d846aca9cd882c293e03eafcc6df",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "e632f21a8bc0c59abc4960482836ac3782db93c0",
              "versionType": "git"
            },
            {
              "lessThan": "5.16",
              "status": "affected",
              "version": "5.15.222",
              "versionType": "semver"
            }
          ]
        },
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/smb/server/mgmt/user_session.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux"
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionStartIncluding": "5.15.222",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: remove stale channels from all sessions on teardown\n\nksmbd_sessions_deregister() removes a connection\u0027s channels from other\nsessions\u0027 channel lists only while conn-\u003ebinding is still set:\n\n\tif (conn-\u003ebinding) {\n\t\thash_for_each_safe(sessions_table, ...)\n\t\t\tksmbd_chann_del(conn, sess);\n\t}\n\nconn-\u003ebinding is a transient flag: it is cleared once a binding\nSESSION_SETUP completes, and also by a subsequent non-binding\nSESSION_SETUP on the same connection (a reauthentication on a bound\nchannel, or a new SessionId==0 setup). A connection that has bound a\nchannel into another session\u0027s ksmbd_chann_list and then clears\nconn-\u003ebinding leaves that channel behind when it disconnects: the\nchannel, whose chann-\u003econn points at the now freed struct ksmbd_conn,\nstays on the owner session\u0027s list.\n\nWhen the owning connection later tears down, the second loop\ndereferences the stale channel:\n\n\txa_for_each(\u0026sess-\u003eksmbd_chann_list, chann_id, chann)\n\t\tif (chann-\u003econn != conn)\n\t\t\tksmbd_conn_set_exiting(chann-\u003econn);   /* freed */\n\nwhich is a use-after-free write into the freed ksmbd_conn (the same\nstale channel is also walked by show_proc_session() through /proc). The\nsession is leaked as well, because its channel list never empties.\n\nRemove the conn-\u003ebinding gate so a connection always removes its\nchannels from every session on teardown."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 8.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - TCP/445 SMB2 SESSION_SETUP messages carry SessionId and SMB2_SESSION_REQ_FLAG_BINDING into smb2_sess_setup(), which calls register_session_channel(); TCP teardown then reaches patched ksmbd_sessions_deregister() through ksmbd_server_terminate_conn().\nAC:L - On a multichannel-enabled server, one client can bind a second connection, send a non-binding SESSION_SETUP to clear conn-\u003ebinding, close it, wait for its ksmbd_conn to be freed, then close the owning connection; no race or third-party state is needed.\nPR:L - smb2_sess_setup() rejects guest binding and requires a valid session; ntlm_authenticate() compares the session user and ksmbd_decode_ntlmssp_auth_blob() verifies the NTLMv2 response before register_session_channel(), requiring valid non-guest SMB credentials.\nUI:N - After authentication, the SMB client alone sends both SESSION_SETUP variants and closes the bound and owning TCP connections; no victim action is required.\nS:U - register_session_channel() stores a kernel ksmbd_conn pointer in a kernel ksmbd_session, and the stale-pointer write in ksmbd_sessions_deregister() corrupts resources within that same kernel security authority.\nC:H - register_session_channel() leaves channel::conn pointing to a freed kmalloc-backed ksmbd_conn; remotely groomed slab reuse followed by the stale dereference creates exploitable kernel memory corruption that can lead to arbitrary kernel-data disclosure.\nI:H - During owner teardown, ksmbd_sessions_deregister() passes the dangling chann-\u003econn to ksmbd_conn_set_exiting(), writing KSMBD_SESS_EXITING into a reused slab object; this UAF corruption can be groomed for kernel data modification or control-flow hijacking.\nA:H - The stale write can corrupt a live slab object and cause an oops or panic; if the slot is reused by another ksmbd_conn, changing its status to KSMBD_SESS_EXITING also terminates that connection, and the sequence is repeatable."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-24T14:09:26.805Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/f8200bb4994e65a2e5c5b314789eeae39078619d"
        },
        {
          "url": "https://git.kernel.org/stable/c/9cd6d714d3ca0cff296542dc989696884e41970f"
        },
        {
          "url": "https://git.kernel.org/stable/c/b145f9b56c87f9c23ad5464ab0844dbc1de12b36"
        },
        {
          "url": "https://git.kernel.org/stable/c/a15cae16f4432a5ad919ee633e31b07178492955"
        },
        {
          "url": "https://git.kernel.org/stable/c/b10665730fbf6b5e45fe422badcbbc3f0df96ef5"
        }
      ],
      "title": "ksmbd: remove stale channels from all sessions on teardown",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-98870",
    "datePublished": "2026-10-23T11:37:07.113Z",
    "dateReserved": "2026-09-25T10:25:14.377Z",
    "dateUpdated": "2026-10-24T14:09:26.805Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-98870",
      "date": "2026-11-12",
      "epss": "0.00544",
      "percentile": "0.46169"
    },
    "nvd": {
      "cve": {
        "affected": [
          {
            "affectedData": [
              {
                "defaultStatus": "unaffected",
                "product": "Linux",
                "programFiles": [
                  "fs/smb/server/mgmt/user_session.c"
                ],
                "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                "vendor": "Linux",
                "versions": [
                  {
                    "lessThan": "f8200bb4994e65a2e5c5b314789eeae39078619d",
                    "status": "affected",
                    "version": "b1b6ed903a6e2b3505a48706bcd499b447ef9e44",
                    "versionType": "git"
                  },
                  {
                    "lessThan": "9cd6d714d3ca0cff296542dc989696884e41970f",
                    "status": "affected",
                    "version": "47b018dba6ec7ebf403fd2d1e713bc7acc9bbb23",
                    "versionType": "git"
                  },
                  {
                    "lessThan": "b145f9b56c87f9c23ad5464ab0844dbc1de12b36",
                    "status": "affected",
                    "version": "9ef4dfd5edbd02f4bf10cd420a30896093d98a67",
                    "versionType": "git"
                  },
                  {
                    "lessThan": "a15cae16f4432a5ad919ee633e31b07178492955",
                    "status": "affected",
                    "version": "5a5b0b7a01fe19b383b3c046546b5ae30c1a7d71",
                    "versionType": "git"
                  },
                  {
                    "lessThan": "b10665730fbf6b5e45fe422badcbbc3f0df96ef5",
                    "status": "affected",
                    "version": "faf8578c77f3d846aca9cd882c293e03eafcc6df",
                    "versionType": "git"
                  },
                  {
                    "status": "affected",
                    "version": "e632f21a8bc0c59abc4960482836ac3782db93c0",
                    "versionType": "git"
                  },
                  {
                    "lessThan": "5.16",
                    "status": "affected",
                    "version": "5.15.222",
                    "versionType": "semver"
                  }
                ]
              },
              {
                "defaultStatus": "unaffected",
                "product": "Linux",
                "programFiles": [
                  "fs/smb/server/mgmt/user_session.c"
                ],
                "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                "vendor": "Linux"
              }
            ],
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
          }
        ],
        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: remove stale channels from all sessions on teardown\n\nksmbd_sessions_deregister() removes a connection\u0027s channels from other\nsessions\u0027 channel lists only while conn-\u003ebinding is still set:\n\n\tif (conn-\u003ebinding) {\n\t\thash_for_each_safe(sessions_table, ...)\n\t\t\tksmbd_chann_del(conn, sess);\n\t}\n\nconn-\u003ebinding is a transient flag: it is cleared once a binding\nSESSION_SETUP completes, and also by a subsequent non-binding\nSESSION_SETUP on the same connection (a reauthentication on a bound\nchannel, or a new SessionId==0 setup). A connection that has bound a\nchannel into another session\u0027s ksmbd_chann_list and then clears\nconn-\u003ebinding leaves that channel behind when it disconnects: the\nchannel, whose chann-\u003econn points at the now freed struct ksmbd_conn,\nstays on the owner session\u0027s list.\n\nWhen the owning connection later tears down, the second loop\ndereferences the stale channel:\n\n\txa_for_each(\u0026sess-\u003eksmbd_chann_list, chann_id, chann)\n\t\tif (chann-\u003econn != conn)\n\t\t\tksmbd_conn_set_exiting(chann-\u003econn);   /* freed */\n\nwhich is a use-after-free write into the freed ksmbd_conn (the same\nstale channel is also walked by show_proc_session() through /proc). The\nsession is leaked as well, because its channel list never empties.\n\nRemove the conn-\u003ebinding gate so a connection always removes its\nchannels from every session on teardown."
          }
        ],
        "id": "CVE-2026-98870",
        "lastModified": "2026-10-24T14:16:47.773",
        "metrics": {
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "LOW",
                "attackVector": "NETWORK",
                "availabilityImpact": "HIGH",
                "baseScore": 8.8,
                "baseSeverity": "HIGH",
                "confidentialityImpact": "HIGH",
                "integrityImpact": "HIGH",
                "privilegesRequired": "LOW",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
                "version": "3.1"
              },
              "exploitabilityScore": 2.8,
              "impactScore": 5.9,
              "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
              "type": "Secondary"
            }
          ]
        },
        "published": "2026-10-23T12:18:20.397",
        "references": [
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/9cd6d714d3ca0cff296542dc989696884e41970f"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/a15cae16f4432a5ad919ee633e31b07178492955"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/b10665730fbf6b5e45fe422badcbbc3f0df96ef5"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/b145f9b56c87f9c23ad5464ab0844dbc1de12b36"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/f8200bb4994e65a2e5c5b314789eeae39078619d"
          }
        ],
        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Received"
      }
    },
    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-11-06T03:17:08+00:00",
      "cve": "CVE-2026-98870",
      "id": "CVE-2026-98870",
      "initial_release_date": "2026-10-23T00:00:00+00:00",
      "product_status:known_not_affected": "202",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: ksmbd: remove stale channels from all sessions on teardown",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-98870.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "important",
      "current_release_date": "2026-10-27T00:43:49Z",
      "cve": "CVE-2026-98870",
      "id": "CVE-2026-98870",
      "initial_release_date": "2026-10-23T23:54:16Z",
      "product_status:known_affected": "126",
      "product_status:known_not_affected": "222",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-98870",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/2026/cve-2026-98870.json",
      "version": "4"
    }
  }
}



Log in or create an account to share your comment.




Tags
Taxonomy of the tags.




Drag nodes to arrange them. Double-click a related vulnerability to open it, or a source to visit its link. The Physics button on the left tunes the layout and the simulation; the legend at the bottom left hides or shows nodes by kind and by sighting type.

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

Author Source Type Date Other

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.
Vulnerability timeline

Sightings and recorded dates, grouped by day · UTC

JSON
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.

Loading timeline…




    Related by attack behaviour

    Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.