{"id":"CVE-2026-89631","title":"smb: client: reject a tree connect response whose byte count is too small","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: reject a tree connect response whose byte count is too small\n\nCIFSTCon() bounds its strnlen() over the byte area with the server's\nByteCount minus two, whi…","severity":"critical","cvss":9.1,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H","cvssSource":"cna","cwe":["CWE-125"],"vendor":"Linux","product":"Linux","affected":["Linux >= cc20c031bb067eb3280a1c4b5c42295093e24863 < d837645a719151ed392d4d9cab4571c2753dab12","Linux >= cc20c031bb067eb3280a1c4b5c42295093e24863 < 2ae219762ebac929bf6ab3473681f10ed566af08","Linux >= cc20c031bb067eb3280a1c4b5c42295093e24863 < 3be89e8039a85fa3b6cd5f9dcc4c1459eb356c2d","Linux >= cc20c031bb067eb3280a1c4b5c42295093e24863 < 411e484fe71a7f1028de617447edad9cb6d9d68a","Linux >= cc20c031bb067eb3280a1c4b5c42295093e24863 < 65deb18359341141d37dc86fc7853511be3c87a7","Linux 2.6.30"],"ssvc":{"exploitation":"none","automatable":"yes","technicalImpact":"partial","timestamp":"2026-10-16T19:24:39.378892Z"},"published":"2026-09-11","updated":"2026-10-21","sourceUpdated":"2026-10-21T12:48:03.355Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-89631","references":[{"url":"https://git.kernel.org/stable/c/d837645a719151ed392d4d9cab4571c2753dab12"},{"url":"https://git.kernel.org/stable/c/2ae219762ebac929bf6ab3473681f10ed566af08"},{"url":"https://git.kernel.org/stable/c/3be89e8039a85fa3b6cd5f9dcc4c1459eb356c2d"},{"url":"https://git.kernel.org/stable/c/411e484fe71a7f1028de617447edad9cb6d9d68a"},{"url":"https://git.kernel.org/stable/c/65deb18359341141d37dc86fc7853511be3c87a7"},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89631.json"},{"url":"https://access.redhat.com/security/cve/CVE-2026-89631"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2532089"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-89631"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-89631"},{"url":"https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-89631.mbox"},{"url":"https://access.redhat.com/errata/RHSA-2026:85321"},{"url":"https://access.redhat.com/errata/RHSA-2026:85773"},{"url":"https://access.redhat.com/errata/RHSA-2026:85774"}],"tags":["cve.org","csaf","vex","red-hat"],"epss":0.00457,"epssPercentile":0.3948,"patched":["10base_smtv","enterprise_linux_appstream_v_10","enterprise_linux_baseos_v_10","enterprise_linux_baseos_v_8","enterprise_linux_codeready_linux_builder_v_10","enterprise_linux_crb_v_8","enterprise_linux_hidden_v_10","enterprise_linux_real_time_for_nfv_v_10","enterprise_linux_nfv_v_8","enterprise_linux_real_time_v_10","enterprise_linux_rt_v_8"],"scores":{"cna":9.1,"vendor":8.1},"ingestedAt":"2026-09-14T15:23:07.474Z","slug":"CVE-2026-89631","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: reject a tree connect response whose byte count is too small\n\nCIFSTCon() bounds its strnlen() over the byte area with the server's\nByteCount minus two, which for ByteCount 0 or 1 goes negative as an int\nand converts to a huge size_t.  The later subtraction wraps the __u16\nbytes_left, and that is what bounds cifs_strndup_from_utf16(): a bound of\nup to 65535 against a ~16 KB cifs_req_poolp object runs off the end of the\nslab object, and the bytes reach userspace through tcon->nativeFileSystem\nin /proc/fs/cifs/DebugData.\n\nReject a byte area too small for what the parser consumes.  Two bytes is\nthe least it can consume, and no conformant response carries fewer.  The\nnew trace point is the 129th smb_eio_trace entry, which __mode(byte)\ncannot represent, so the attribute goes with it.\n\n## Affected\n\n- `Linux >= cc20c031bb067eb3280a1c4b5c42295093e24863 < d837645a719151ed392d4d9cab4571c2753dab12`\n- `Linux >= cc20c031bb067eb3280a1c4b5c42295093e24863 < 2ae219762ebac929bf6ab3473681f10ed566af08`\n- `Linux >= cc20c031bb067eb3280a1c4b5c42295093e24863 < 3be89e8039a85fa3b6cd5f9dcc4c1459eb356c2d`\n- `Linux >= cc20c031bb067eb3280a1c4b5c42295093e24863 < 411e484fe71a7f1028de617447edad9cb6d9d68a`\n- `Linux >= cc20c031bb067eb3280a1c4b5c42295093e24863 < 65deb18359341141d37dc86fc7853511be3c87a7`\n- `Linux 2.6.30`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.\n\n## Vendor advisories\n\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-2026:85773** · Red Hat · fixed in: Red Hat Enterprise Linux BaseOS (v. 8), Red Hat Enterprise Linux CRB (v. 8) · released 2026-10-20 · [advisory](https://access.redhat.com/errata/RHSA-2026:85773)\n- **RHSA-2026:85774** · Red Hat · fixed in: Red Hat Enterprise Linux NFV (v. 8), Red Hat Enterprise Linux RT (v. 8) · released 2026-10-20 · [advisory](https://access.redhat.com/errata/RHSA-2026:85774)\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-2026-89631.json)","depth":"midnight","depthScore":50,"depthScoreParts":{"impact":50.1,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[{"seq":227216,"id":"CVE-2026-89631","ts":1792587305687,"field":"cvss","old":"8.1","new":"9.1"},{"seq":227215,"id":"CVE-2026-89631","ts":1792587305687,"field":"severity","old":"high","new":"critical"},{"seq":225735,"id":"CVE-2026-89631","ts":1792498402599,"field":"cvss","old":"9.1","new":"8.1"},{"seq":225734,"id":"CVE-2026-89631","ts":1792498402599,"field":"severity","old":"critical","new":"high"},{"seq":223272,"id":"CVE-2026-89631","ts":1792180037625,"field":"cvss","old":"8.1","new":"9.1"},{"seq":223271,"id":"CVE-2026-89631","ts":1792180037625,"field":"severity","old":"high","new":"critical"},{"seq":211565,"id":"CVE-2026-89631","ts":1790495172604,"field":"cvss","old":"7","new":"8.1"},{"seq":208079,"id":"CVE-2026-89631","ts":1789922705728,"field":"cvss","old":"5.7","new":"7"},{"seq":208078,"id":"CVE-2026-89631","ts":1789922705728,"field":"severity","old":"medium","new":"high"},{"seq":202845,"id":"CVE-2026-89631","ts":1789403732644,"field":"cvss","old":"9.1","new":"5.7"},{"seq":202844,"id":"CVE-2026-89631","ts":1789403732644,"field":"severity","old":"critical","new":"medium"},{"seq":197830,"id":"CVE-2026-89631","ts":1789384320579,"field":"cvss","old":"5.7","new":"9.1"},{"seq":197829,"id":"CVE-2026-89631","ts":1789384320579,"field":"severity","old":"medium","new":"critical"},{"seq":183395,"id":"CVE-2026-89631","ts":1789356675185,"field":"cvss","old":"9.1","new":"5.7"},{"seq":183394,"id":"CVE-2026-89631","ts":1789356675185,"field":"severity","old":"critical","new":"medium"},{"seq":153466,"id":"CVE-2026-89631","ts":1789285350623,"field":"cvss","old":null,"new":"9.1"},{"seq":153465,"id":"CVE-2026-89631","ts":1789285350623,"field":"severity","old":"none","new":"critical"},{"seq":147696,"id":"CVE-2026-89631","ts":1789270211920,"field":"cvss","old":null,"new":"5.7"},{"seq":147695,"id":"CVE-2026-89631","ts":1789270211920,"field":"severity","old":"none","new":"medium"},{"seq":109452,"id":"CVE-2026-89631","ts":1789183731968,"field":"cvss","old":null,"new":"5.7"},{"seq":109451,"id":"CVE-2026-89631","ts":1789183731968,"field":"severity","old":"none","new":"medium"}]}