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CVE-2026-89788

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National Vulnerability Database Information

Description: In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix tree connection use-after-free in smb2_tree_connect() ksmbd_tree_conn_connect() publishes a new tree connection in sess->tree_conns with a single reference and returns its pointer to smb2_tree_connect(). The handler continues to initialize the object and build the response after publication. A concurrent session logoff can erase the connection and drop that reference, freeing the object while the handler still uses it. BUG: KASAN: slab-use-after-free in smb2_tree_connect+0xe3d/0xf90 smb2_tree_connect (fs/smb/server/smb2pdu.c:2872) handle_ksmbd_work process_one_work worker_thread kthread After xa_store() succeeds, take a second reference before releasing tree_conns_lock. The original reference belongs to the xarray entry and the second belongs to the creating smb2_tree_connect() handler. Keep the references balanced in every path: - On normal exit or an error after publication, smb2_tree_connect() drops its creator reference. Error cleanup also calls ksmbd_tree_conn_disconnect(), which drops the xarray reference only if it removes the exact entry. - SMB2 TREE_DISCONNECT uses the same helper to remove the entry and drop its xarray reference. The request's existing lookup reference remains owned by the request and is released by the existing cleanup. - Session LOGOFF removes each entry and drops its xarray reference. If it wins the race, later cleanup sees that the entry is gone and does not drop that reference again. To enforce this ownership, claim the disconnected state and erase the exact entry atomically under tree_conns_lock. This guarantees one drop for the xarray reference and one drop by each in-flight user, regardless of which teardown path wins. If logoff removes the entry before initialization completes, fail the connect instead of marking the detached object TREE_CONNECTED.

CVSS Base Score: 9.8 (v3.1)

The CVSS Base Score is a score from 0 to 10 that represents the intrinsic severity of a vulnerability. A higher score indicates greater severity.

Value
0.02.55.07.510.0
Published on: 09/16/2026 09:17:09
Last modified: 09/16/2026 15:18:09
NIST: CVE source from the National Vulnerability Database (NVD)

CVSS Metrics Details

  • Base Severity: CRITICAL
  • Attack Vector: NETWORK
  • Attack Complexity: LOW
  • Privileges Required: NONE
  • User Interaction: NONE
  • Scope: UNCHANGED
  • Confidentiality Impact: HIGH
  • Integrity Impact: HIGH
  • Availability Impact: HIGH

FIRST Information

EPSS Score: 0.0052

The EPSS (Exploit Prediction Scoring System) is a score from 0 to 1 that indicates the probability that a vulnerability will be exploited in the real world in the next 30 days. A higher value indicates a greater likelihood of exploitation.

Value
0.00.250.50.751.0

Percentile: 0.4286

The Percentile indicates how much higher this vulnerability's EPSS score is compared to all other vulnerabilities in the EPSS database. For example, a percentile of 0.90 (90%) means that 90% of vulnerabilities have an EPSS score equal to or lower than the current one.

Value
0.00.250.50.751.0

*Data updated as of: 2026-09-18


CISA Information (Known Exploited Vulnerabilities)

The CISA KEV Catalog lists vulnerabilities that have been actively exploited in the real world. If a CVE is present in this catalog, it indicates that the threat is immediate and mitigation should be a top priority.

CVE CVE-2026-89788 is not present in the CISA KEV Catalog. This indicates that it is not currently classified by CISA as an actively exploited vulnerability.


Articles published on Red Hot Cyber

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Exploit PoC from GitHub

No results found on GitHub for this CVE.