{"api_version":"1","generated_at":"2026-10-27T04:32:03+00:00","cve":"CVE-2026-89630","urls":{"html":"https://cve.report/CVE-2026-89630","api":"https://cve.report/api/cve/CVE-2026-89630.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-89630","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-89630"},"summary":{"title":"smb: client: restore the data_offset bound in is_valid_oplock_break()","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: restore the data_offset bound in is_valid_oplock_break()\n\nCommit 83bfbd0bb902 (\"cifs: Remove the RFC1002 header from smb_hdr\")\nchanged the quantity this bound is measured against.  It used to be\nsrv->total_read minus the 4-byte RFC1002 preamble that total_read then\nincluded, so it was the SMB message length.  The same commit stopped\ncounting the preamble, and the mechanical substitution to\nsrv->total_read - srv->pdu_size left an expression that is identically\nzero: standard_receive3() reads MID_HEADER_SIZE() bytes and then exactly\npdu_length - MID_HEADER_SIZE() more, adding both to total_read.\n\nlen is therefore 0, the subtraction below it wraps, and no __u32\nDataOffset can exceed the result, so the check from commit 097f5863b1a0\n(\"cifs: read overflow in is_valid_oplock_break()\") no longer rejects\nanything.  Use total_read, which is now the message length on its own.","state":"PUBLISHED","assigner":"Linux","published_at":"2026-09-11 20:19:48","updated_at":"2026-10-19 09:17:59"},"problem_types":[],"metrics":[{"version":"3.1","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","type":"Secondary","score":"9.1","severity":"CRITICAL","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H","data":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H","baseScore":9.1,"baseSeverity":"CRITICAL","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"NONE","availabilityImpact":"HIGH"}},{"version":"3.1","source":"CNA","type":"DECLARED","score":"9.1","severity":"CRITICAL","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H","data":{"baseScore":9.1,"baseSeverity":"CRITICAL","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H","version":"3.1"}}],"references":[{"url":"https://git.kernel.org/stable/c/ba22f575de9deeae4ae0859ca4315a7698226237","name":"https://git.kernel.org/stable/c/ba22f575de9deeae4ae0859ca4315a7698226237","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/5b16a1967a01ad4496a7206a87c3eb16f1df2b05","name":"https://git.kernel.org/stable/c/5b16a1967a01ad4496a7206a87c3eb16f1df2b05","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-89630","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-89630","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 83bfbd0bb9025f98fa62b44f93bd67466773d1db 5b16a1967a01ad4496a7206a87c3eb16f1df2b05 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 83bfbd0bb9025f98fa62b44f93bd67466773d1db ba22f575de9deeae4ae0859ca4315a7698226237 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 78e718c5aa146063cd70d2cc68297c3ac41f31ee git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 6.18.56 6.19 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 6.19","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.19 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.2.4 7.2.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.3 * original_commit_for_fix","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":{"cve_year":"2026","cve_id":"89630","cve":"CVE-2026-89630","epss":"0.005390000","percentile":"0.437030000","score_date":"2026-10-12","updated_at":"2026-10-13 00:11:16"},"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"cna":{"affected":[{"defaultStatus":"unaffected","product":"Linux","programFiles":["fs/smb/client/smb1misc.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"lessThan":"5b16a1967a01ad4496a7206a87c3eb16f1df2b05","status":"affected","version":"83bfbd0bb9025f98fa62b44f93bd67466773d1db","versionType":"git"},{"lessThan":"ba22f575de9deeae4ae0859ca4315a7698226237","status":"affected","version":"83bfbd0bb9025f98fa62b44f93bd67466773d1db","versionType":"git"},{"status":"affected","version":"78e718c5aa146063cd70d2cc68297c3ac41f31ee","versionType":"git"},{"lessThan":"6.19","status":"affected","version":"6.18.56","versionType":"semver"}]},{"defaultStatus":"affected","product":"Linux","programFiles":["fs/smb/client/smb1misc.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"status":"affected","version":"6.19"},{"lessThan":"6.19","status":"unaffected","version":"0","versionType":"semver"},{"lessThanOrEqual":"7.2.*","status":"unaffected","version":"7.2.4","versionType":"semver"},{"lessThanOrEqual":"*","status":"unaffected","version":"7.3","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.2.4","versionStartIncluding":"6.19","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.3","versionStartIncluding":"6.19","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.18.56","vulnerable":true}],"negate":false,"operator":"OR"}]}],"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: restore the data_offset bound in is_valid_oplock_break()\n\nCommit 83bfbd0bb902 (\"cifs: Remove the RFC1002 header from smb_hdr\")\nchanged the quantity this bound is measured against.  It used to be\nsrv->total_read minus the 4-byte RFC1002 preamble that total_read then\nincluded, so it was the SMB message length.  The same commit stopped\ncounting the preamble, and the mechanical substitution to\nsrv->total_read - srv->pdu_size left an expression that is identically\nzero: standard_receive3() reads MID_HEADER_SIZE() bytes and then exactly\npdu_length - MID_HEADER_SIZE() more, adding both to total_read.\n\nlen is therefore 0, the subtraction below it wraps, and no __u32\nDataOffset can exceed the result, so the check from commit 097f5863b1a0\n(\"cifs: read overflow in is_valid_oplock_break()\") no longer rejects\nanything.  Use total_read, which is now the message length on its own."}],"metrics":[{"cvssV3_1":{"baseScore":9.1,"baseSeverity":"CRITICAL","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H","version":"3.1"},"scenarios":[{"lang":"en","value":"AV:N - The flaw is in the in-kernel SMB1 client demultiplex path: a remote peer sends an unsolicited SMB_COM_NT_TRANSACT response over TCP/445 and cifs_demultiplex_thread() calls is_valid_oplock_break() on unmatched frames, so a malicious or compromised SMB server (or MITM) reaches it via network protocol data.\nAC:L - The attacker fully controls Command, Flags, ByteCount, and DataOffset in a single unsolicited frame; the broken bound wraps so any DataOffset is accepted and the resulting heap over-read is deterministic, with no race or condition the attacker cannot influence once the client is on the SMB1 connection.\nPR:N - A matching MID, session setup, or tree connect is not required: after negotiate, an unmatched NT_TRANSACT+RESPONSE frame is treated as an oplock/dnotify break before authentication, so the malicious server needs no credentials or privileges on the client host.\nUI:N - On a persistent SMB1 mount (cifsroot, automount, or an already-mounted legacy NAS share) the cifsd thread processes unsolicited frames after the existing connection or reconnect, so no additional victim action is required at attack time.\nS:U - The out-of-bounds/use-after-free read occurs in kernel heap used by the CIFS client on the same host kernel security authority and does not cross a VM, IOMMU, or sandbox boundary.\nC:H - Attacker-controlled DataOffset displaces file_notify_information into adjacent or freed cifs_small_rq slab objects (KASAN use-after-free read), and printing FileName with %s can walk unbounded kernel memory, so the disclosure is not limited to a few bounded bytes.\nI:N - The displaced pointer is only read (Action and FileName for a debug print); the bug does not write through that pointer or otherwise provide a kernel memory-modification or control-flow primitive.\nA:H - The KASAN-confirmed slab use-after-free and unmapped over-read run in the cifsd demultiplex thread and can oops or panic the kernel, and a malicious peer can repeat the unsolicited frame to retrigger the crash."}]}],"providerMetadata":{"dateUpdated":"2026-10-19T08:50:02.437Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/5b16a1967a01ad4496a7206a87c3eb16f1df2b05"},{"url":"https://git.kernel.org/stable/c/ba22f575de9deeae4ae0859ca4315a7698226237"}],"title":"smb: client: restore the data_offset bound in is_valid_oplock_break()","x_generator":{"engine":"bippy-1.2.0"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-89630","datePublished":"2026-09-11T19:45:25.697Z","dateReserved":"2026-09-11T19:38:34.738Z","dateUpdated":"2026-10-19T08:50:02.437Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-09-11 20:19:48","lastModifiedDate":"2026-10-19 09:17:59","problem_types":[],"metrics":{"cvssMetricV31":[{"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","type":"Secondary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H","baseScore":9.1,"baseSeverity":"CRITICAL","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"NONE","availabilityImpact":"HIGH"},"exploitabilityScore":3.9,"impactScore":5.2}]},"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"89630","Ordinal":"1","Title":"smb: client: restore the data_offset bound in is_valid_oplock_br","CVE":"CVE-2026-89630","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"89630","Ordinal":"1","NoteData":"In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: restore the data_offset bound in is_valid_oplock_break()\n\nCommit 83bfbd0bb902 (\"cifs: Remove the RFC1002 header from smb_hdr\")\nchanged the quantity this bound is measured against.  It used to be\nsrv->total_read minus the 4-byte RFC1002 preamble that total_read then\nincluded, so it was the SMB message length.  The same commit stopped\ncounting the preamble, and the mechanical substitution to\nsrv->total_read - srv->pdu_size left an expression that is identically\nzero: standard_receive3() reads MID_HEADER_SIZE() bytes and then exactly\npdu_length - MID_HEADER_SIZE() more, adding both to total_read.\n\nlen is therefore 0, the subtraction below it wraps, and no __u32\nDataOffset can exceed the result, so the check from commit 097f5863b1a0\n(\"cifs: read overflow in is_valid_oplock_break()\") no longer rejects\nanything.  Use total_read, which is now the message length on its own.","Type":"Description","Title":"smb: client: restore the data_offset bound in is_valid_oplock_br"}]}}}