CVE-2026-89633

{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-89633", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-11T19:38:34.739Z", "datePublished": "2026-09-11T19:45:28.083Z", "dateUpdated": "2026-10-30T12:32:22.744Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-30T12:32:22.744Z"}, "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: fix OOB read/write from unvalidated DataOffset in coalesce_t2()\n\ncoalesce_t2() computes data pointers directly from server-supplied\nDataOffset fields with no validation against buffer bounds:\n\n data_area_of_tgt = (char *)&pSMBt->hdr.Protocol +\n get_unaligned_le16(&pSMBt->t2_rsp.DataOffset);\n data_area_of_src = (char *)&pSMBs->hdr.Protocol +\n get_unaligned_le16(&pSMBs->t2_rsp.DataOffset);\n data_area_of_tgt += total_in_tgt;\n ...\n memcpy(data_area_of_tgt, data_area_of_src, total_in_src);\n\nA small DataOffset can push a pointer below the actual byte area,\noverwriting header fields; a large one can push it past the buffer\nend, causing out-of-bounds heap reads (source) or writes (target).\nThe BCC overflow guard does not prevent this: BCC reflects how much\ndata is present, while DataOffset controls where in the buffer it\nstarts.\n\nThe \"validate target area\" comment present since the function was\nfirst written in 2005 was a placeholder that was never implemented.\n\nAdd lower- and upper-bound checks for both data pointers before the\nmemcpy, and before any target header fields are modified."}], "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 - coalesce_t2() runs in cifs_demultiplex_thread on SMB1 TRANS2 responses received over TCP/445; a malicious or compromised SMB1 server (or MITM on an unsigned session) delivers the crafted DataOffset/DataCount fields entirely over the network.\nAC:L - The server fully controls DataOffset, DataCount, and TotalDataCount in both primary and secondary TRANS2 PDUs and can force a large first fragment so mid->resp_buf is set; the unbounded memcpy is deterministic with no race or condition outside the attacker\u2019s control.\nPR:N - The attacker is the remote SMB peer and needs no account or privileges on the victim; coalesce_t2() runs in the demux thread before validate_t2() or any local capability check, and session credentials belong to the client mount, not the attacking server.\nUI:N - Once an SMB1 CIFS mount exists (fstab, autofs, embedded/industrial NAS; CONFIG_CIFS_ALLOW_INSECURE_LEGACY defaults on), reconnect and ordinary lookup/readdir/getattr plus cifs_qfs_tcon QUERY_FS_INFO issue TRANS2 automatically, so the server can trigger coalescing with no further user action.\nS:U - The out-of-bounds heap read/write corrupts the client kernel\u2019s own cifs_request slab within the same host security authority; this is not a VM escape, IOMMU bypass, or sandbox boundary crossing.\nC:H - An unvalidated source DataOffset lets memcpy read far past the secondary response (DataOffset is a 16-bit value up to 65535 versus a ~16KB cifs_request object), disclosing adjacent kernel heap; the same memory-corruption primitive can be leveraged for further disclosure.\nI:H - An unvalidated target DataOffset lets memcpy write attacker-controlled bytes past the primary buffer (or backward into the SMB header); the BCC-size guard does not constrain where the copy starts, yielding an out-of-bounds write exploitable for control-flow hijacking.\nA:H - Reading or writing tens of kilobytes past the cifs_request allocation can fault on unmapped pages and oops or panic the demux thread, and a malicious server can retrigger it on every multi-part TRANS2."}]}], "affected": [{"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["fs/smb/client/smb1transport.c"], "versions": [{"version": "e4eb295d38b57f4d4b956942a48887eb252d97c6", "lessThan": "f7baf60435129e3a5f3500a38e3cb4c3860deed7", "status": "affected", "versionType": "git"}, {"version": "e4eb295d38b57f4d4b956942a48887eb252d97c6", "lessThan": "9f3a7440731a34c89ad04fef6616f185acb28401", "status": "affected", "versionType": "git"}, {"version": "e4eb295d38b57f4d4b956942a48887eb252d97c6", "lessThan": "531ac35abd74fb5b4aec5e19543e832613a1789d", "status": "affected", "versionType": "git"}, {"version": "e4eb295d38b57f4d4b956942a48887eb252d97c6", "lessThan": "6eb70b78e48b0031bd1a05fe1b58959a48e87739", "status": "affected", "versionType": "git"}, {"version": "e4eb295d38b57f4d4b956942a48887eb252d97c6", "lessThan": "36d01415d881d5326a0dd3384f781cd7e69aff2d", "status": "affected", "versionType": "git"}, {"version": "e4eb295d38b57f4d4b956942a48887eb252d97c6", "lessThan": "672cf86aa6aa0fb4012ce4c3b3498df42ad67a4e", "status": "affected", "versionType": "git"}, {"version": "e4eb295d38b57f4d4b956942a48887eb252d97c6", "lessThan": "033bc80019f07d158630df4e69b19a49010f54f1", "status": "affected", "versionType": "git"}, {"version": "e4eb295d38b57f4d4b956942a48887eb252d97c6", "lessThan": "6343c1da561962688f203362d80d6a3bfa39fa1b", "status": "affected", "versionType": "git"}]}, {"product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["fs/smb/client/smb1transport.c"], "versions": [{"version": "2.6.12", "status": "affected"}, {"version": "0", "lessThan": "2.6.12", "status": "unaffected", "versionType": "semver"}, {"version": "5.10.273", "lessThanOrEqual": "5.10.*", "status": "unaffected", "versionType": "semver"}, {"version": "5.15.224", "lessThanOrEqual": "5.15.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.1.191", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.6.160", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.12.113", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.18.51", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver"}, {"version": "7.2.4", "lessThanOrEqual": "7.2.*", "status": "unaffected", "versionType": "semver"}, {"version": "7.3", "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": "2.6.12", "versionEndExcluding": "5.10.273"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.12", "versionEndExcluding": "5.15.224"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.12", "versionEndExcluding": "6.1.191"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.12", "versionEndExcluding": "6.6.160"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.12", "versionEndExcluding": "6.12.113"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.12", "versionEndExcluding": "6.18.51"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.12", "versionEndExcluding": "7.2.4"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.12", "versionEndExcluding": "7.3"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/f7baf60435129e3a5f3500a38e3cb4c3860deed7"}, {"url": "https://git.kernel.org/stable/c/9f3a7440731a34c89ad04fef6616f185acb28401"}, {"url": "https://git.kernel.org/stable/c/531ac35abd74fb5b4aec5e19543e832613a1789d"}, {"url": "https://git.kernel.org/stable/c/6eb70b78e48b0031bd1a05fe1b58959a48e87739"}, {"url": "https://git.kernel.org/stable/c/36d01415d881d5326a0dd3384f781cd7e69aff2d"}, {"url": "https://git.kernel.org/stable/c/672cf86aa6aa0fb4012ce4c3b3498df42ad67a4e"}, {"url": "https://git.kernel.org/stable/c/033bc80019f07d158630df4e69b19a49010f54f1"}, {"url": "https://git.kernel.org/stable/c/6343c1da561962688f203362d80d6a3bfa39fa1b"}], "title": "smb: client: fix OOB read/write from unvalidated DataOffset in coalesce_t2()", "x_generator": {"engine": "bippy-1.2.0"}}}}

{}

{"affected": [{"affectedData": [{"defaultStatus": "unaffected", "product": "Linux", "programFiles": ["fs/smb/client/smb1transport.c"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"lessThan": "f7baf60435129e3a5f3500a38e3cb4c3860deed7", "status": "affected", "version": "e4eb295d38b57f4d4b956942a48887eb252d97c6", "versionType": "git"}, {"lessThan": "9f3a7440731a34c89ad04fef6616f185acb28401", "status": "affected", "version": "e4eb295d38b57f4d4b956942a48887eb252d97c6", "versionType": "git"}, {"lessThan": "531ac35abd74fb5b4aec5e19543e832613a1789d", "status": "affected", "version": "e4eb295d38b57f4d4b956942a48887eb252d97c6", "versionType": "git"}, {"lessThan": "6eb70b78e48b0031bd1a05fe1b58959a48e87739", "status": "affected", "version": "e4eb295d38b57f4d4b956942a48887eb252d97c6", "versionType": "git"}, {"lessThan": "36d01415d881d5326a0dd3384f781cd7e69aff2d", "status": "affected", "version": "e4eb295d38b57f4d4b956942a48887eb252d97c6", "versionType": "git"}, {"lessThan": "672cf86aa6aa0fb4012ce4c3b3498df42ad67a4e", "status": "affected", "version": "e4eb295d38b57f4d4b956942a48887eb252d97c6", "versionType": "git"}, {"lessThan": "033bc80019f07d158630df4e69b19a49010f54f1", "status": "affected", "version": "e4eb295d38b57f4d4b956942a48887eb252d97c6", "versionType": "git"}, {"lessThan": "6343c1da561962688f203362d80d6a3bfa39fa1b", "status": "affected", "version": "e4eb295d38b57f4d4b956942a48887eb252d97c6", "versionType": "git"}]}, {"defaultStatus": "affected", "product": "Linux", "programFiles": ["fs/smb/client/smb1transport.c"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"status": "affected", "version": "2.6.12"}, {"lessThan": "2.6.12", "status": "unaffected", "version": "0", "versionType": "semver"}, {"lessThanOrEqual": "5.10.*", "status": "unaffected", "version": "5.10.273", "versionType": "semver"}, {"lessThanOrEqual": "5.15.*", "status": "unaffected", "version": "5.15.224", "versionType": "semver"}, {"lessThanOrEqual": "6.1.*", "status": "unaffected", "version": "6.1.191", "versionType": "semver"}, {"lessThanOrEqual": "6.6.*", "status": "unaffected", "version": "6.6.160", "versionType": "semver"}, {"lessThanOrEqual": "6.12.*", "status": "unaffected", "version": "6.12.113", "versionType": "semver"}, {"lessThanOrEqual": "6.18.*", "status": "unaffected", "version": "6.18.51", "versionType": "semver"}, {"lessThanOrEqual": "7.2.*", "status": "unaffected", "version": "7.2.4", "versionType": "semver"}, {"lessThanOrEqual": "*", "status": "unaffected", "version": "7.3", "versionType": "original_commit_for_fix"}]}], "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}], "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: fix OOB read/write from unvalidated DataOffset in coalesce_t2()\n\ncoalesce_t2() computes data pointers directly from server-supplied\nDataOffset fields with no validation against buffer bounds:\n\n data_area_of_tgt = (char *)&pSMBt->hdr.Protocol +\n get_unaligned_le16(&pSMBt->t2_rsp.DataOffset);\n data_area_of_src = (char *)&pSMBs->hdr.Protocol +\n get_unaligned_le16(&pSMBs->t2_rsp.DataOffset);\n data_area_of_tgt += total_in_tgt;\n ...\n memcpy(data_area_of_tgt, data_area_of_src, total_in_src);\n\nA small DataOffset can push a pointer below the actual byte area,\noverwriting header fields; a large one can push it past the buffer\nend, causing out-of-bounds heap reads (source) or writes (target).\nThe BCC overflow guard does not prevent this: BCC reflects how much\ndata is present, while DataOffset controls where in the buffer it\nstarts.\n\nThe \"validate target area\" comment present since the function was\nfirst written in 2005 was a placeholder that was never implemented.\n\nAdd lower- and upper-bound checks for both data pointers before the\nmemcpy, and before any target header fields are modified."}], "id": "CVE-2026-89633", "lastModified": "2026-10-30T13:20:23.223", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "HIGH", "baseScore": 9.8, "baseSeverity": "CRITICAL", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H", "version": "3.1"}, "exploitabilityScore": 3.9, "impactScore": 5.9, "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "type": "Secondary"}]}, "published": "2026-09-11T20:19:48.887", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/033bc80019f07d158630df4e69b19a49010f54f1"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/36d01415d881d5326a0dd3384f781cd7e69aff2d"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/531ac35abd74fb5b4aec5e19543e832613a1789d"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/6343c1da561962688f203362d80d6a3bfa39fa1b"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/672cf86aa6aa0fb4012ce4c3b3498df42ad67a4e"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/6eb70b78e48b0031bd1a05fe1b58959a48e87739"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/9f3a7440731a34c89ad04fef6616f185acb28401"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/f7baf60435129e3a5f3500a38e3cb4c3860deed7"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Received"}

{"bugzilla": {"description": "kernel: Linux kernel SMB client: Out-of-bounds read/write via unvalidated DataOffset", "id": "2532230", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2532230"}, "csaw": false, "cvss3": {"cvss3_base_score": "7.1", "cvss3_scoring_vector": "CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:H", "status": "draft"}, "cwe": "CWE-125", "details": ["A flaw was found in the Linux kernel's Server Message Block (SMB) client. The `coalesce_t2()` function processes server-supplied `DataOffset` fields without proper validation against buffer boundaries. A remote attacker could exploit this by crafting malicious SMB responses. This could lead to out-of-bounds read and write operations, potentially resulting in information disclosure or arbitrary code execution."], "name": "CVE-2026-89633", "public_date": "2026-09-11T19:45:28Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-89633\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-89633\nhttps://git.kernel.org/stable/c/033bc80019f07d158630df4e69b19a49010f54f1\nhttps://git.kernel.org/stable/c/6343c1da561962688f203362d80d6a3bfa39fa1b\nhttps://git.kernel.org/stable/c/672cf86aa6aa0fb4012ce4c3b3498df42ad67a4e"], "threat_severity": "Important"}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "code_commit", "value": "[e4eb295d38b57f4d4b956942a48887eb252d97c6,672cf86aa6aa0fb4012ce4c3b3498df42ad67a4e)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "code_commit", "value": "[e4eb295d38b57f4d4b956942a48887eb252d97c6,033bc80019f07d158630df4e69b19a49010f54f1)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "code_commit", "value": "[e4eb295d38b57f4d4b956942a48887eb252d97c6,6343c1da561962688f203362d80d6a3bfa39fa1b)"}}], "enrichment": {"confidence": 99.0, "confidence_source": "inferred", "scores": [{"score": 99.0, "source": "inferred"}, {"score": 100.0, "source": "matching"}]}, "original": {"product": "Linux", "source": "cna", "vendor": "Linux"}, "product": "linux_kernel", "vendor": "linux"}, {"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "2.6.12"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "semver", "value": "[0,2.6.12)"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "semver", "value": "[6.18.51,6.19.0)"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "semver", "value": "[7.2.4,7.3.0)"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "semver", "value": "[7.3-rc1,*]"}}], "enrichment": {"confidence": 99.0, "confidence_source": "inferred", "scores": [{"score": 99.0, "source": "inferred"}, {"score": 100.0, "source": "matching"}]}, "original": {"product": "Linux", "source": "cna", "vendor": "Linux"}, "product": "linux_kernel", "vendor": "linux"}], "created": "2026-09-12T06:30:09.005487+00:00", "updated": "2026-09-15T21:15:14.619996+00:00", "vendors": ["linux", "linux$PRODUCT$linux_kernel"]}