{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2025-40285", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2025-04-16T07:20:57.184Z", "datePublished": "2025-12-06T21:51:09.590Z", "dateUpdated": "2026-08-05T12:09:15.214Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T12:09:15.214Z" }, "descriptions": [ { "lang": "en", "value": "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()." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "baseScore": 7.5, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "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 — it pipelines the SESSION_SETUP requests that take the reference and issues the LOGOFF/PreviousSessionId request that flips conn->status to NEED_RECONNECT — 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 — 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." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/smb/server/smb2pdu.c" ], "versions": [ { "version": "37a0e2b362b3150317fb6e2139de67b1e29ae5ff", "lessThan": "6fc935f798d44a8eb8a5e6659198399fbf57b981", "status": "affected", "versionType": "git" }, { "version": "450a844c045ff0895d41b05a1cbe8febd1acfcfd", "lessThan": "e671f9bb97805771380c98de944e2ceab6949188", "status": "affected", "versionType": "git" }, { "version": "a39e31e22a535d47b14656a7d6a893c7f6cf758c", "lessThan": "dcc51dfe6ff26b52cac106865a172ac982d78401", "status": "affected", "versionType": "git" }, { "version": "b95629435b84b9ecc0c765995204a4d8a913ed52", "lessThan": "d37b2c81c83d6c0d5ca582f4fe73c672983f9e0d", "status": "affected", "versionType": "git" }, { "version": "b95629435b84b9ecc0c765995204a4d8a913ed52", "lessThan": "379510a815cb2e64eb0a379cb62295d6ade65df0", "status": "affected", "versionType": "git" }, { "version": "2107ab40629aeabbec369cf34b8cf0f288c3eb1b", "status": "affected", "versionType": "git" }, { "version": "6.1.121", "lessThan": "6.1.159", "status": "affected", "versionType": "semver" }, { "version": "6.6.67", "lessThan": "6.6.117", "status": "affected", "versionType": "semver" }, { "version": "6.12.6", "lessThan": "6.12.59", "status": "affected", "versionType": "semver" }, { "version": "5.15.176", "lessThan": "5.16", "status": "affected", "versionType": "semver" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/smb/server/smb2pdu.c" ], "versions": [ { "version": "6.13", "status": "affected" }, { "version": "0", "lessThan": "6.13", "status": "unaffected", "versionType": "semver" }, { "version": "6.1.159", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.117", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.59", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.17.9", "lessThanOrEqual": "6.17.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] } ], "cpeApplicability": [ { "nodes": [ { "operator": "OR", "negate": false, "cpeMatch": [ { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.1.121", "versionEndExcluding": "6.1.159" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.6.67", "versionEndExcluding": "6.6.117" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.12.6", "versionEndExcluding": "6.12.59" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.13", "versionEndExcluding": "6.17.9" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.13", "versionEndExcluding": "6.18" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.15.176" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/6fc935f798d44a8eb8a5e6659198399fbf57b981" }, { "url": "https://git.kernel.org/stable/c/e671f9bb97805771380c98de944e2ceab6949188" }, { "url": "https://git.kernel.org/stable/c/dcc51dfe6ff26b52cac106865a172ac982d78401" }, { "url": "https://git.kernel.org/stable/c/d37b2c81c83d6c0d5ca582f4fe73c672983f9e0d" }, { "url": "https://git.kernel.org/stable/c/379510a815cb2e64eb0a379cb62295d6ade65df0" } ], "title": "smb/server: fix possible refcount leak in smb2_sess_setup()", "x_generator": { "engine": "bippy-1.2.0" } } } }