{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-72422", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-08-09T03:40:39.927Z", "datePublished": "2026-08-15T05:56:41.090Z", "dateUpdated": "2026-08-17T05:44:02.758Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-17T05:44:02.758Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: fix use-after-free of conn->preauth_info in concurrent SMB2 NEGOTIATE\n\nconn->preauth_info is shared connection state (struct\npreauth_integrity_info, kmalloc-96) that is allocated and freed by the\nSMB2 NEGOTIATE handler and read by the response send path.\n\nsmb2_handle_negotiate() allocates conn->preauth_info, and on a\ndeassemble_neg_contexts() failure kfrees it and sets it to NULL. Both the\nallocation and the free/NULL happen under ksmbd_conn_lock(conn) (the\nconnection srv_mutex), which is held across the whole handler body.\n\nThe response send path smb3_preauth_hash_rsp(), called from the send:\nblock of __handle_ksmbd_work(), reads conn->preauth_info and dereferences\nconn->preauth_info->Preauth_HashValue (via\nksmbd_gen_preauth_integrity_hash()) without taking conn_lock. When a\nclient drives two SMB2 NEGOTIATE requests on the same connection, one\nworker can free conn->preauth_info on the failing-negotiate path while a\nconcurrent send-path worker is reading it, producing a slab\nuse-after-free read (KASAN-confirmed).\n\nThe send-path read tested conn->preauth_info for NULL but raced with the\nfree that occurs between the NULL check and the dereference, so the NULL\nguard alone does not close the window.\n\nSerialize the NEGOTIATE-branch read in smb3_preauth_hash_rsp() under\nksmbd_conn_lock(conn) and re-check conn->preauth_info inside the lock.\nBecause the negotiate handler holds conn_lock across its kfree + NULL\nassignment, a reader that also takes conn_lock either runs fully before\nthe allocation or fully after the NULL store, and can never observe the\nfreed-but-not-yet-NULLed pointer. ksmbd_gen_preauth_integrity_hash()\ntakes no locks itself (it only computes a SHA-512 over the buffer), so\nno lock-ordering inversion is introduced, and conn_lock is a sleepable\nmutex which is safe on this send path (it already performs network I/O)." } ], "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 bug is in ksmbd's SMB2 NEGOTIATE handler reachable by any remote client over TCP port 445 without local access; exploitation requires only crafted SMB 3.1.1 negotiate packets on an established network connection.\nAC:L - The attacker controls both sides of the race by pipelining two SMB2 NEGOTIATE requests on the same connection, with one crafted to fail deassemble_neg_contexts() and free preauth_info while the other is in the response send path; KASAN-confirmed UAF with no uncontrollable timing.\nPR:N - SMB2 NEGOTIATE is processed before any authentication or session establishment; smb2_check_user_session explicitly exempts NEGOTIATE from session validation, so an unauthenticated remote attacker can reach the vulnerable code path.\nUI:N - Exploitation requires only network packets sent by the attacker to an exposed ksmbd instance; no victim user action such as mounting a share or opening a file is needed.\nS:U - Successful exploitation compromises kernel memory on the SMB server host itself; this is standard in-kernel memory corruption without crossing a VM, container, or IOMMU security boundary to a separate authority.\nC:H - KASAN-confirmed slab use-after-free read of conn->preauth_info (kmalloc-96) via Preauth_HashValue and Preauth_HashId dereference; UAF on attacker-influenced freed heap memory enables arbitrary kernel memory disclosure through heap grooming.\nI:H - The UAF corrupts kernel heap state on a network-facing pre-auth path; freed preauth_integrity_info objects can be reallocated via heap spraying to obtain arbitrary write or control-flow hijack primitives beyond the immediate hash-buffer access.\nA:H - Concurrent UAF read of freed conn->preauth_info during smb3_preauth_hash_rsp() causes kernel oops or panic (KASAN-confirmed); even without full exploitation the race reliably triggers high-severity denial of service on the server." } ] } ], "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": "dd4e4c811898410e6a3ae3b63207b7c542860907", "lessThan": "c7bef84740d1d57848c74f6f5b996606e43ea4fe", "status": "affected", "versionType": "git" }, { "version": "aa7253c2393f6dcd6a1468b0792f6da76edad917", "lessThan": "d0a469122e7bf8338fec1949fb1e8e1290ed8caa", "status": "affected", "versionType": "git" }, { "version": "aa7253c2393f6dcd6a1468b0792f6da76edad917", "lessThan": "7470511d085af1c7a043a60e53d52b512d5a10b1", "status": "affected", "versionType": "git" }, { "version": "aa7253c2393f6dcd6a1468b0792f6da76edad917", "lessThan": "16a1ecf39c217e3d164bd32ef2a4f650abc067fa", "status": "affected", "versionType": "git" }, { "version": "aa7253c2393f6dcd6a1468b0792f6da76edad917", "lessThan": "77bb0bbfcc4e777ca653174689e5e363f8ee63d1", "status": "affected", "versionType": "git" }, { "version": "aa7253c2393f6dcd6a1468b0792f6da76edad917", "lessThan": "1c89da3baa2b1f269178afa87dc30479b8535776", "status": "affected", "versionType": "git" }, { "version": "aa7253c2393f6dcd6a1468b0792f6da76edad917", "lessThan": "0c054227479ed7e36ebccb3a558bc0ef698264f6", "status": "affected", "versionType": "git" }, { "version": "8a8315a5960bd2b5ffc75f44fc089e57c3b17c44", "status": "affected", "versionType": "git" }, { "version": "ff20f1875889dbe4a67c9298e609d7c88cf6456d", "status": "affected", "versionType": "git" }, { "version": "5.15.61", "lessThan": "5.15.212", "status": "affected", "versionType": "semver" }, { "version": "5.18.18", "lessThan": "5.19", "status": "affected", "versionType": "semver" }, { "version": "5.19.2", "lessThan": "5.20", "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": "6.0", "status": "affected" }, { "version": "0", "lessThan": "6.0", "status": "unaffected", "versionType": "semver" }, { "version": "5.15.212", "lessThanOrEqual": "5.15.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.1.178", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.145", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.97", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.40", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.1.5", "lessThanOrEqual": "7.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.2", "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": "5.15.61", "versionEndExcluding": "5.15.212" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.0", "versionEndExcluding": "6.1.178" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.0", "versionEndExcluding": "6.6.145" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.0", "versionEndExcluding": "6.12.97" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.0", "versionEndExcluding": "6.18.40" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.0", "versionEndExcluding": "7.1.5" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.0", "versionEndExcluding": "7.2" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.18.18" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.19.2" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/c7bef84740d1d57848c74f6f5b996606e43ea4fe" }, { "url": "https://git.kernel.org/stable/c/d0a469122e7bf8338fec1949fb1e8e1290ed8caa" }, { "url": "https://git.kernel.org/stable/c/7470511d085af1c7a043a60e53d52b512d5a10b1" }, { "url": "https://git.kernel.org/stable/c/16a1ecf39c217e3d164bd32ef2a4f650abc067fa" }, { "url": "https://git.kernel.org/stable/c/77bb0bbfcc4e777ca653174689e5e363f8ee63d1" }, { "url": "https://git.kernel.org/stable/c/1c89da3baa2b1f269178afa87dc30479b8535776" }, { "url": "https://git.kernel.org/stable/c/0c054227479ed7e36ebccb3a558bc0ef698264f6" } ], "title": "ksmbd: fix use-after-free of conn->preauth_info in concurrent SMB2 NEGOTIATE", "x_generator": { "engine": "bippy-1.2.0" } } } }