{"id":"CVE-2026-89661","title":"kernel: NFSD: Prevent post-shutdown use-after-free in unlock_filesystem (CVE-2026-89661)","summary":"A flaw was found in the Linux kernel's Network File System Daemon (NFSD). A local administrator with CAP_SYS_ADMIN capabilities can trigger a use-after-free vulnerability by writing to /proc/fs/nfsd/unlock_filesystem after the NFSD server …","severity":"medium","cvss":5.5,"cvssVector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","cvssSource":"vendor","cwe":"CWE-825","vendor":"Red Hat","product":"Red Hat Enterprise Linux 10","affected":["enterprise_linux 10","enterprise_linux 6"],"published":"2026-09-11","updated":"2026-09-16","sourceUpdated":"2026-09-16T05:50:10+00:00","source":"CSAF","sourceUrl":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89661.json","references":[{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89661.json"},{"url":"https://access.redhat.com/security/cve/CVE-2026-89661"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2532346"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-89661"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-89661"},{"url":"https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-89661.mbox"},{"url":"https://git.kernel.org/stable/c/0c1a755b7212e0835398d4df5e782ea85ccd7476"},{"url":"https://git.kernel.org/stable/c/292d915d3ba6fd15eeb88351fa10581683073109"}],"tags":["csaf","vex","red-hat","cve.org"],"epss":0.00189,"epssPercentile":0.08808,"ingestedAt":"2026-09-14T11:11:19.886Z","slug":"CVE-2026-89661","body":"## Overview\n\nA flaw was found in the Linux kernel's Network File System Daemon (NFSD). A local administrator with CAP_SYS_ADMIN capabilities can trigger a use-after-free vulnerability by writing to /proc/fs/nfsd/unlock_filesystem after the NFSD server has shut down. This can lead to memory corruption, potentially causing a denial of service.\n\n## Vendor advisories\n\n- **Red Hat VEX** · Moderate · affected: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 6 · no fix planned: Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 10 · updated 2026-09-16 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89661.json)\n\n**kernel: NFSD: Prevent post-shutdown use-after-free in unlock_filesystem** — rated Moderate by Red Hat. Released 2026-09-11, updated 2026-09-16.\n\nAffected:\n\n- Red Hat Enterprise Linux 10\n- Red Hat Enterprise Linux 6\n\nNo fix planned:\n\n- Red Hat Enterprise Linux 6\n- Red Hat Enterprise Linux 10\n\nNot affected:\n\n- Red Hat Enterprise Linux 7\n- Red Hat Enterprise Linux 8\n- Red Hat Enterprise Linux 9\n- Red Hat OpenShift Container Platform 4\n\n## Remediation\n\nOut of support scope","depth":"sunlit","depthScore":30,"depthScoreParts":{"impact":30.3,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[{"seq":205493,"id":"CVE-2026-89661","ts":1789576721976,"field":"cvss","old":"4.1","new":"5.5"},{"seq":203998,"id":"CVE-2026-89661","ts":1789490230978,"field":"cvss","old":null,"new":"4.1"},{"seq":203997,"id":"CVE-2026-89661","ts":1789490230978,"field":"severity","old":"none","new":"medium"},{"seq":147343,"id":"CVE-2026-89661","ts":1789270210534,"field":"cvss","old":null,"new":"4.1"},{"seq":147342,"id":"CVE-2026-89661","ts":1789270210534,"field":"severity","old":"none","new":"medium"},{"seq":109096,"id":"CVE-2026-89661","ts":1789183730290,"field":"cvss","old":null,"new":"4.1"},{"seq":109095,"id":"CVE-2026-89661","ts":1789183730290,"field":"severity","old":"none","new":"medium"}]}