{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2023-54076", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2025-12-24T12:21:05.093Z", "datePublished": "2025-12-24T12:23:18.330Z", "dateUpdated": "2026-08-05T09:16:59.986Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T09:16:59.986Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: fix missed ses refcounting\n\nUse new cifs_smb_ses_inc_refcount() helper to get an active reference\nof @ses and @ses->dfs_root_ses (if set). This will prevent\n@ses->dfs_root_ses of being put in the next call to cifs_put_smb_ses()\nand thus potentially causing an use-after-free bug." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H", "baseScore": 9.8, "baseSeverity": "CRITICAL" }, "scenarios": [ { "lang": "en", "value": "AV:N - The flaw is in the in-kernel SMB/CIFS network filesystem client, and the unbalanced puts are driven by data from the remote peer — the server picks the SMB2.0/2.1 dialect that routes signing through the buggy `smb2_calc_signature()`, returns the DFS referrals (`DFSREF_REFERRAL_SERVER`) that populate `ses->dfs_root_ses`, and controls the delayed CREATE replies that reach `smb2_handle_cancelled_mid()`. A malicious, compromised, or MITM'd SMB/DFS server drives the refcount underflow purely over the network.\nAC:L - The imbalance is deterministic, not a race: every `smb2_find_smb_ses_unlocked()` acquisition drops one extra reference on `ses->dfs_root_ses` at release, so the attacker simply drives enough signed exchanges to force the count to zero. No memory-layout or timing condition outside the attacker's control is needed.\nPR:N - The attacker is the remote SMB/DFS server (or a network MITM) and holds no privileges or account on the victim client; referral responses and dialect negotiation happen without any credential on the target system.\nUI:N - The `smb2transport.c` half of the bug is a steady-state runtime path — on an already-mounted DFS share, signature calculation, cancelled-MID handling, echo keepalives and the DFS cache refresh worker accumulate the extra puts with no user action at attack time.\nS:U - The premature free and subsequent corruption are confined to kernel memory within the same security authority; no VM, IOMMU, or sandbox boundary is crossed.\nC:H - Use-after-free on a `cifs_ses` object whose slot can be reoccupied by attacker-groomed heap data yields a read primitive, and the freed session still holds authentication material (`auth_key.response`, signing keys) and kernel pointers used by subsequent code.\nI:H - After the free, `cifs_put_smb_ses()` reads `ses->server` from freed memory and performs an indirect call via `server->ops->logoff()`, giving a control-flow hijack primitive; heap spraying over the freed `cifs_ses` converts this into arbitrary write/code execution.\nA:H - The refcount underflow frees a session still referenced by child sessions, tcons, and the DFS cache worker, reliably producing an oops/panic (and a `WARN_ON(ses->ses_count < 0)`) that takes down the machine." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/smb/client/dfs.c", "fs/smb/client/smb2transport.c" ], "versions": [ { "version": "8e3554150d6c80a84b3cb046615d1a0e943811dc", "lessThan": "eb382196e6f6e05cfafdab797840e5a96c6e7bf0", "status": "affected", "versionType": "git" }, { "version": "8e3554150d6c80a84b3cb046615d1a0e943811dc", "lessThan": "bf99f6be2d20146942bce6f9e90a0ceef12cbc1e", "status": "affected", "versionType": "git" }, { "version": "f30d226bcc9f0e2d97b4a6e94c43a28148fbeab6", "status": "affected", "versionType": "git" }, { "version": "c082c3be0f96e759ff2e361d929832fda0b93851", "status": "affected", "versionType": "git" }, { "version": "6.2.15", "lessThan": "6.3", "status": "affected", "versionType": "semver" }, { "version": "6.3.2", "lessThan": "6.4", "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/client/dfs.c", "fs/smb/client/smb2transport.c" ], "versions": [ { "version": "6.4", "status": "affected" }, { "version": "0", "lessThan": "6.4", "status": "unaffected", "versionType": "semver" }, { "version": "6.4.7", "lessThanOrEqual": "6.4.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.5", "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": "6.4", "versionEndExcluding": "6.4.7" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.4", "versionEndExcluding": "6.5" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.2.15" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.3.2" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/eb382196e6f6e05cfafdab797840e5a96c6e7bf0" }, { "url": "https://git.kernel.org/stable/c/bf99f6be2d20146942bce6f9e90a0ceef12cbc1e" } ], "title": "smb: client: fix missed ses refcounting", "x_generator": { "engine": "bippy-1.2.0" } } } }