{ "schema_version": "1.6.1", "id": "RPI-CVE-2025-40285", "modified": "2026-10-09T11:39:44Z", "upstream": [ "CVE-2025-40285" ], "published": "2025-12-06T21:53:16Z", "summary": "smb/server: fix possible refcount leak in smb2_sess_setup()", "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nsmb/server: fix possible refcount leak in smb2_sess_setup()\n\nReference count of ksmbd_session will leak when session need reconnect.\nFix this by adding the missing ksmbd_user_session_put().", "severity": [ { "type": "CVSS_V3", "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H" } ], "affected": [ { "package": { "ecosystem": "Raspberry Pi OS:12", "name": "linux" }, "versions": [ "1:6.6.74-1+rpt1", "1:6.12.20-1+rpt1~bpo12+1", "1:6.12.25-1+rpt1", "1:6.12.34-1+rpt1~bookworm", "1:6.12.47-1+rpt1~bookworm" ], "ecosystem_specific": { "binaries": [ { "binary_name": "linux-image-6.6.74+rpt-rpi-2712", "binary_version": "1:6.6.74-1+rpt1" }, { "binary_name": 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"https://www.cve.org/CVERecord?id=CVE-2025-40285" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/6fc935f798d44a8eb8a5e6659198399fbf57b981" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/e671f9bb97805771380c98de944e2ceab6949188" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/dcc51dfe6ff26b52cac106865a172ac982d78401" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/d37b2c81c83d6c0d5ca582f4fe73c672983f9e0d" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/379510a815cb2e64eb0a379cb62295d6ade65df0" } ], "database_specific": { "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git", "upstream_modified": "2026-08-05T12:19:11Z", "severity": { "source": "kernel CNA", "cvss_v3_score": 7.5, "cvss_v3_severity": "High", "scenario": "AV:N - ksmbd is the in-kernel SMB server on TCP/445, and the leak is driven entirely by remote SMB2 SESSION_SETUP and LOGOFF PDUs on the attacker's own TCP connections. No local access to the target is required.\nAC:L - The attacker controls both sides of the race \u2014 it pipelines the SESSION_SETUP requests that take the reference and issues the LOGOFF/PreviousSessionId request that flips conn->status to NEED_RECONNECT \u2014 and the window is wide because ksmbd_conn_wait_idle()/ksmbd_conn_wait_idle_sess_id() hold that status for the duration of the teardown (up to 120 s). Failed attempts are harmless and can be retried indefinitely.\nPR:N - smb2_check_user_session() explicitly bypasses session validation for SMB2_SESSION_SETUP, and the session is registered in conn->sessions before any credential check, so the leaking lookup is reached with zero credentials. On the common guest-mapped ksmbd share, ntlm_authenticate() skips password verification for user_guest(), so the LOGOFF that flips the connection to NEED_RECONNECT is also available unauthenticated.\nUI:N - The attacker opens its own connections and issues every request itself; no legitimate user or administrator action is involved.\nS:U - The leaked session object and its pinned file references are kernel resources within the same security authority as the ksmbd server; no VM, IOMMU, or sandbox boundary is crossed.\nC:N - Nothing is read out of bounds and nothing is transmitted back to the client on this error path \u2014 the only effect is that a reference count is never decremented, so no kernel data is disclosed.\nI:N - No memory is written out of bounds or freed early; the object simply outlives its intended lifetime, so no kernel data or control flow is modified.\nA:H - Each won race permanently leaks a struct ksmbd_session plus its entire file table, so open struct file/inode/dentry references are pinned forever (also blocking unmount), and the attack is replayable without limit over surviving connections, driving unbounded kernel memory and handle exhaustion to OOM and system hang." } } }