{"id":"CVE-2026-89633","title":"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 …","summary":"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 …","severity":"critical","cvss":9.8,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","cwe":["CWE-125"],"vendor":"Linux","product":"Linux","affected":["Linux >= e4eb295d38b57f4d4b956942a48887eb252d97c6 < 36d01415d881d5326a0dd3384f781cd7e69aff2d","Linux >= e4eb295d38b57f4d4b956942a48887eb252d97c6 < 672cf86aa6aa0fb4012ce4c3b3498df42ad67a4e","Linux >= e4eb295d38b57f4d4b956942a48887eb252d97c6 < 033bc80019f07d158630df4e69b19a49010f54f1","Linux >= e4eb295d38b57f4d4b956942a48887eb252d97c6 < 6343c1da561962688f203362d80d6a3bfa39fa1b","Linux 2.6.12"],"published":"2026-09-11","updated":"2026-10-15","sourceUpdated":"2026-10-15T11:17:54.450","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-89633","references":[{"url":"https://git.kernel.org/stable/c/033bc80019f07d158630df4e69b19a49010f54f1","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/36d01415d881d5326a0dd3384f781cd7e69aff2d","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/6343c1da561962688f203362d80d6a3bfa39fa1b","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/672cf86aa6aa0fb4012ce4c3b3498df42ad67a4e","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89633.json"},{"url":"https://access.redhat.com/security/cve/CVE-2026-89633"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2532230"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-89633"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-89633"},{"url":"https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-89633.mbox"},{"url":"https://access.redhat.com/errata/RHSA-2026:85321"},{"url":"https://access.redhat.com/errata/RHSA-2026:86033"},{"url":"https://git.kernel.org/stable/c/6eb70b78e48b0031bd1a05fe1b58959a48e87739"}],"tags":["nvd","cve.org","csaf","vex","red-hat"],"epss":0.00491,"epssPercentile":0.41974,"scores":{"nvd":9.8,"cna":9.8,"vendor":8},"ingestedAt":"2026-09-14T15:23:07.474Z","patched":["10base_smtv","enterprise_linux_appstream_v_10","enterprise_linux_appstream_v_9","enterprise_linux_baseos_v_10","enterprise_linux_baseos_v_9","enterprise_linux_codeready_linux_builder_v_10","enterprise_linux_codeready_linux_builder_v_9","enterprise_linux_hidden_v_10","enterprise_linux_real_time_for_nfv_v_10","enterprise_linux_real_time_for_nfv_v_9","enterprise_linux_real_time_v_10","enterprise_linux_real_time_v_9"],"slug":"CVE-2026-89633","body":"## Overview\n\nIn 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.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.\n\n## Vendor advisories\n\n- **Red Hat VEX** · Important · affected: Red Hat Enterprise Linux 9 · no fix planned: Red Hat Enterprise Linux 9 · updated 2026-10-20 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89633.json)\n- **RHSA-2026:85321** · Red Hat · fixed in: 10Base-SMTV, Red Hat Enterprise Linux AppStream (v. 10), Red Hat Enterprise Linux BaseOS (v. 10), Red Hat Enterprise Linux CodeReady Linux Builder (v. 10), Red Hat Enterprise Linux Hidden (v. 10), Red Hat Enterprise Linux Real Time for NFV (v. 10), … · released 2026-10-19 · [advisory](https://access.redhat.com/errata/RHSA-2026:85321)\n- **RHSA-2026:86033** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream (v. 9), Red Hat Enterprise Linux BaseOS (v. 9), Red Hat Enterprise Linux CodeReady Linux Builder (v. 9), Red Hat Enterprise Linux Real Time for NFV (v. 9), Red Hat Enterprise Linux Real Time (v. 9) · released 2026-10-20 · [advisory](https://access.redhat.com/errata/RHSA-2026:86033)","depth":"midnight","depthScore":54,"depthScoreParts":{"impact":53.9,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[{"seq":222162,"id":"CVE-2026-89633","ts":1792062149805,"field":"cvss","old":"8","new":"9.8"},{"seq":222161,"id":"CVE-2026-89633","ts":1792062149805,"field":"severity","old":"high","new":"critical"},{"seq":211824,"id":"CVE-2026-89633","ts":1790581655034,"field":"cvss","old":"7","new":"8"},{"seq":208114,"id":"CVE-2026-89633","ts":1789922715445,"field":"cvss","old":"7.1","new":"7"},{"seq":203011,"id":"CVE-2026-89633","ts":1789403733340,"field":"cvss","old":"9.8","new":"7.1"},{"seq":203010,"id":"CVE-2026-89633","ts":1789403733340,"field":"severity","old":"critical","new":"high"},{"seq":197836,"id":"CVE-2026-89633","ts":1789384320603,"field":"cvss","old":"7.1","new":"9.8"},{"seq":197835,"id":"CVE-2026-89633","ts":1789384320603,"field":"severity","old":"high","new":"critical"},{"seq":183729,"id":"CVE-2026-89633","ts":1789356677133,"field":"cvss","old":"9.8","new":"7.1"},{"seq":183728,"id":"CVE-2026-89633","ts":1789356677133,"field":"severity","old":"critical","new":"high"},{"seq":153470,"id":"CVE-2026-89633","ts":1789285350646,"field":"cvss","old":null,"new":"9.8"},{"seq":153469,"id":"CVE-2026-89633","ts":1789285350646,"field":"severity","old":"none","new":"critical"},{"seq":147586,"id":"CVE-2026-89633","ts":1789270211491,"field":"cvss","old":null,"new":"7.1"},{"seq":147585,"id":"CVE-2026-89633","ts":1789270211491,"field":"severity","old":"none","new":"high"},{"seq":109342,"id":"CVE-2026-89633","ts":1789183731509,"field":"cvss","old":null,"new":"7.1"},{"seq":109341,"id":"CVE-2026-89633","ts":1789183731509,"field":"severity","old":"none","new":"high"}]}