{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2025-71070", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-01-13T15:30:19.647Z", "datePublished": "2026-01-13T15:31:24.709Z", "dateUpdated": "2026-08-05T12:11:51.227Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T12:11:51.227Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nublk: clean up user copy references on ublk server exit\n\nIf a ublk server process releases a ublk char device file, any requests\ndispatched to the ublk server but not yet completed will retain a ref\nvalue of UBLK_REFCOUNT_INIT. Before commit e63d2228ef83 (\"ublk: simplify\naborting ublk request\"), __ublk_fail_req() would decrement the reference\ncount before completing the failed request. However, that commit\noptimized __ublk_fail_req() to call __ublk_complete_rq() directly\nwithout decrementing the request reference count.\nThe leaked reference count incorrectly allows user copy and zero copy\noperations on the completed ublk request. It also triggers the\nWARN_ON_ONCE(refcount_read(&io->ref)) warnings in ublk_queue_reinit()\nand ublk_deinit_queue().\nCommit c5c5eb24ed61 (\"ublk: avoid ublk_io_release() called after ublk\nchar dev is closed\") already fixed the issue for ublk devices using\nUBLK_F_SUPPORT_ZERO_COPY or UBLK_F_AUTO_BUF_REG. However, the reference\ncount leak also affects UBLK_F_USER_COPY, the other reference-counted\ndata copy mode. Fix the condition in ublk_check_and_reset_active_ref()\nto include all reference-counted data copy modes. This ensures that any\nublk requests still owned by the ublk server when it exits have their\nreference counts reset to 0." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 7.8, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:L - Exploitation uses local close, io_uring, and pread/pwrite operations on a ublk character device; no network or physical path reaches the flaw.\nAC:L - A malicious server can control the outstanding I/O, server exit, request generation, and concurrent copy/commit operations. It can park the dispatch task or stall user copying, so the relevant race does not depend on uncontrollable conditions.\nPR:L - The data-plane open/read/write path has no capability check and explicitly supports non-CAP_SYS_ADMIN daemon tasks when device-node access is delegated. Device provisioning and recovery require initial-namespace CAP_SYS_ADMIN, but a low-privileged daemon account can exploit an already managed USER_COPY device.\nUI:N - The attacker can generate the necessary block I/O and server shutdown/recovery sequence without another user's action.\nS:U - The vulnerable ublk code and the affected kernel memory and execution context belong to the same kernel security authority.\nC:H - The stale reference can permit a copy before dispatch resets the refcount, after which concurrent completion can free or reuse bio, bvec, and request pages still being traversed. A pread operation can therefore disclose broadly controllable freed or reallocated kernel-backed memory.\nI:H - A concurrent pwrite can operate through freed or attacker-groomed bio/bvec state, providing a path to corrupt reused pages or redirect writes to kernel memory and potentially hijack control flow.\nA:H - The resulting use-after-free can cause an oops or kernel panic, and the deterministic WARN_ON_ONCE sites can also panic systems configured with panic-on-warn." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "drivers/block/ublk_drv.c" ], "versions": [ { "version": "e63d2228ef831af36f963b3ab8604160cfff84c1", "lessThan": "13456b4f1033d911f8bf3a0a1195656f293ba0f6", "status": "affected", "versionType": "git" }, { "version": "e63d2228ef831af36f963b3ab8604160cfff84c1", "lessThan": "daa24603d9f0808929514ee62ced30052ca7221c", "status": "affected", "versionType": "git" }, { "version": "e537193fc4a43b48ac51cc6366319e15e32dd540", "status": "affected", "versionType": "git" }, { "version": "6.14.6", "lessThan": "6.15", "status": "affected", "versionType": "semver" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "drivers/block/ublk_drv.c" ], "versions": [ { "version": "6.15", "status": "affected" }, { "version": "0", "lessThan": "6.15", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.3", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.19", "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": "6.15", "versionEndExcluding": "6.18.3" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.15", "versionEndExcluding": "6.19" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.14.6" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/13456b4f1033d911f8bf3a0a1195656f293ba0f6" }, { "url": "https://git.kernel.org/stable/c/daa24603d9f0808929514ee62ced30052ca7221c" } ], "title": "ublk: clean up user copy references on ublk server exit", "x_generator": { "engine": "bippy-1.2.0" } } } }