{"id":"CVE-2026-89771","title":"ring-buffer: Fix subbuf resize race with ring buffer readers","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nring-buffer: Fix subbuf resize race with ring buffer readers\n\ntrace_buffer subbuf_size is read lockless in ring_buffer_read_page() and\nring_buffer_read_start(), while i…","severity":"high","cvss":7.8,"cvssVector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","cvssSource":"cna","cwe":["CWE-366"],"vendor":"Linux","product":"Linux","affected":["Linux >= f9b94daa542a8d2532f0930f01cd9aec2d19621b < 6d666f0b8b36c0765cf19fbe6de5a7ba5a73aad9","Linux >= f9b94daa542a8d2532f0930f01cd9aec2d19621b < 50f4a793c4ff24826efb0ac700989a5063cc53df","Linux >= f9b94daa542a8d2532f0930f01cd9aec2d19621b < 0c7c517827a453128a8f58bfd849546a29813b27","Linux >= f9b94daa542a8d2532f0930f01cd9aec2d19621b < 8a5f63637890f03177146efddaba5ec7a1b4d61f","Linux 6.8"],"published":"2026-09-11","updated":"2026-10-19","sourceUpdated":"2026-10-19T08:52:24.715Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-89771","references":[{"url":"https://git.kernel.org/stable/c/6d666f0b8b36c0765cf19fbe6de5a7ba5a73aad9"},{"url":"https://git.kernel.org/stable/c/50f4a793c4ff24826efb0ac700989a5063cc53df"},{"url":"https://git.kernel.org/stable/c/0c7c517827a453128a8f58bfd849546a29813b27"},{"url":"https://git.kernel.org/stable/c/8a5f63637890f03177146efddaba5ec7a1b4d61f"},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89771.json"},{"url":"https://access.redhat.com/security/cve/CVE-2026-89771"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2532138"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-89771"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-89771"},{"url":"https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-89771.mbox"}],"tags":["cve.org","csaf","vex","red-hat","score-dispute"],"epss":0.0012,"epssPercentile":0.01798,"scores":{"cna":7.8,"vendor":5.5},"ingestedAt":"2026-09-14T15:23:07.472Z","slug":"CVE-2026-89771","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nring-buffer: Fix subbuf resize race with ring buffer readers\n\ntrace_buffer subbuf_size is read lockless in ring_buffer_read_page() and\nring_buffer_read_start(), while it can simultaneously be resized with\nring_buffer_subbuf_order_set().\n\nInstead of trace_buffer::subbuf_size, use bpage::order in\nring_buffer_read_start() and ring_buffer_read_page().\n\nIn ring_buffer_read_start(), even with resize_disabled, there is still a\npossibility of a race with a buffer modification. Hold the trace_buffer\nmutex to synchronise with any pending ring buffer order modification.\n\ntrace_buffer::subbuf_size is now actually useless, remove it. Also,\ncreate accessors rb_subbuf_capacity() and rb_page_capacity() which\nreturn the actual size available for storing events, while\nrb_subbuf_size() returns the actual subbuf page-size.\n\n## Affected\n\n- `Linux >= f9b94daa542a8d2532f0930f01cd9aec2d19621b < 6d666f0b8b36c0765cf19fbe6de5a7ba5a73aad9`\n- `Linux >= f9b94daa542a8d2532f0930f01cd9aec2d19621b < 50f4a793c4ff24826efb0ac700989a5063cc53df`\n- `Linux >= f9b94daa542a8d2532f0930f01cd9aec2d19621b < 0c7c517827a453128a8f58bfd849546a29813b27`\n- `Linux >= f9b94daa542a8d2532f0930f01cd9aec2d19621b < 8a5f63637890f03177146efddaba5ec7a1b4d61f`\n- `Linux 6.8`\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** · Moderate · affected: Red Hat Enterprise Linux 10, Red Hat OpenShift Container Platform 4 · no fix planned: Red Hat Enterprise Linux 10, Red Hat OpenShift Container Platform 4 · updated 2026-09-15 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89771.json)","depth":"twilight","depthScore":43,"depthScoreParts":{"impact":42.9,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[{"seq":224560,"id":"CVE-2026-89771","ts":1792401408510,"field":"cvss","old":"5.5","new":"7.8"},{"seq":224559,"id":"CVE-2026-89771","ts":1792401408510,"field":"severity","old":"medium","new":"high"},{"seq":205526,"id":"CVE-2026-89771","ts":1789576723478,"field":"cvss","old":"4.7","new":"5.5"},{"seq":202950,"id":"CVE-2026-89771","ts":1789403733081,"field":"cvss","old":"7.8","new":"4.7"},{"seq":202949,"id":"CVE-2026-89771","ts":1789403733081,"field":"severity","old":"high","new":"medium"},{"seq":197653,"id":"CVE-2026-89771","ts":1789384318252,"field":"cvss","old":"4.7","new":"7.8"},{"seq":197652,"id":"CVE-2026-89771","ts":1789384318252,"field":"severity","old":"medium","new":"high"},{"seq":183639,"id":"CVE-2026-89771","ts":1789356676215,"field":"cvss","old":"7.8","new":"4.7"},{"seq":183638,"id":"CVE-2026-89771","ts":1789356676215,"field":"severity","old":"high","new":"medium"},{"seq":153660,"id":"CVE-2026-89771","ts":1789285351841,"field":"cvss","old":null,"new":"7.8"},{"seq":153659,"id":"CVE-2026-89771","ts":1789285351841,"field":"severity","old":"none","new":"high"},{"seq":147678,"id":"CVE-2026-89771","ts":1789270211849,"field":"cvss","old":null,"new":"4.7"},{"seq":147677,"id":"CVE-2026-89771","ts":1789270211849,"field":"severity","old":"none","new":"medium"},{"seq":109426,"id":"CVE-2026-89771","ts":1789183731867,"field":"cvss","old":null,"new":"4.7"},{"seq":109425,"id":"CVE-2026-89771","ts":1789183731867,"field":"severity","old":"none","new":"medium"}]}