{"id":"CVE-2026-89637","title":"kernel: smb: client: fix UAF and buffer leak in cifs_check_trans2() for malformed secondary T2 (CVE-2026-89637)","summary":"A flaw was found in the Linux kernel's Server Message Block (SMB) client. When processing a malformed secondary TRANSACT2 response, a use-after-free (UAF) vulnerability and a buffer leak can occur in the `cifs_check_trans2()` function. Thi…","severity":"high","cvss":7,"cvssVector":"CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H","cvssSource":"vendor","cwe":"CWE-825","vendor":"Red Hat","product":"Red Hat Enterprise Linux 9","affected":["enterprise_linux 10","enterprise_linux 9","openshift_container_platform 4"],"published":"2026-09-11","updated":"2026-09-18","sourceUpdated":"2026-09-18T22:00:04+00:00","source":"CSAF","sourceUrl":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89637.json","references":[{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89637.json"},{"url":"https://access.redhat.com/security/cve/CVE-2026-89637"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2532405"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-89637"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-89637"},{"url":"https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-89637.mbox"},{"url":"https://git.kernel.org/stable/c/5e6533a683f6a851158d9f33fb4ea8f4f25d7f84"},{"url":"https://git.kernel.org/stable/c/730d0bb19507b9e19c2fe5343109ac618e2fbce5"},{"url":"https://git.kernel.org/stable/c/9eed72e9534b10a6d9f8f5146feff3db53aebdba"}],"tags":["csaf","vex","red-hat","cve.org","score-dispute"],"epss":0.00588,"epssPercentile":0.46568,"scores":{"vendor":7,"cna":9.8},"ingestedAt":"2026-09-14T15:23:07.476Z","slug":"CVE-2026-89637","body":"## Overview\n\nA flaw was found in the Linux kernel's Server Message Block (SMB) client. When processing a malformed secondary TRANSACT2 response, a use-after-free (UAF) vulnerability and a buffer leak can occur in the `cifs_check_trans2()` function. This can lead to a dangling buffer being reused by the demux thread, potentially allowing an attacker to achieve arbitrary code execution or cause a denial of service.\n\n## Vendor advisories\n\n- **Red Hat VEX** · Moderate · affected: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 9, Red Hat OpenShift Container Platform 4 · no fix planned: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 9, Red Hat OpenShift Container Platform 4 · updated 2026-09-18 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89637.json)\n\n**kernel: smb: client: fix UAF and buffer leak in cifs_check_trans2() for malformed secondary T2** — rated Moderate by Red Hat. Released 2026-09-11, updated 2026-09-18.\n\nAffected:\n\n- Red Hat Enterprise Linux 10\n- Red Hat Enterprise Linux 9\n- Red Hat OpenShift Container Platform 4\n\nNo fix planned:\n\n- Red Hat Enterprise Linux 10\n- Red Hat Enterprise Linux 9\n- Red Hat OpenShift Container Platform 4\n\nNot affected:\n\n- Red Hat Enterprise Linux 6\n- Red Hat Enterprise Linux 7\n- Red Hat Enterprise Linux 8\n- Red Hat OpenShift Container Platform 4\n\n## Remediation\n\nAffected","depth":"twilight","depthScore":39,"depthScoreParts":{"impact":38.5,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[{"seq":206926,"id":"CVE-2026-89637","ts":1789749703101,"field":"cvss","old":"7.1","new":"7"},{"seq":203007,"id":"CVE-2026-89637","ts":1789403733324,"field":"cvss","old":"9.8","new":"7.1"},{"seq":203006,"id":"CVE-2026-89637","ts":1789403733324,"field":"severity","old":"critical","new":"high"},{"seq":197817,"id":"CVE-2026-89637","ts":1789384320524,"field":"cvss","old":"7.1","new":"9.8"},{"seq":197816,"id":"CVE-2026-89637","ts":1789384320524,"field":"severity","old":"high","new":"critical"},{"seq":183762,"id":"CVE-2026-89637","ts":1789356677280,"field":"cvss","old":"9.8","new":"7.1"},{"seq":183761,"id":"CVE-2026-89637","ts":1789356677280,"field":"severity","old":"critical","new":"high"},{"seq":153478,"id":"CVE-2026-89637","ts":1789285350678,"field":"cvss","old":null,"new":"9.8"},{"seq":153477,"id":"CVE-2026-89637","ts":1789285350678,"field":"severity","old":"none","new":"critical"},{"seq":147257,"id":"CVE-2026-89637","ts":1789270204938,"field":"cvss","old":null,"new":"7.1"},{"seq":147256,"id":"CVE-2026-89637","ts":1789270204938,"field":"severity","old":"none","new":"high"},{"seq":109004,"id":"CVE-2026-89637","ts":1789183729916,"field":"cvss","old":null,"new":"7.1"},{"seq":109003,"id":"CVE-2026-89637","ts":1789183729916,"field":"severity","old":"none","new":"high"}]}