{"id":"CVE-2026-97420","title":"In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: NUL-terminate replaced sysctl value\n\nWhen writing to sysctls, proc_sys_call_handler() guarantees that the\nbuffer passed to proc handlers is NUL-terminated","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: NUL-terminate replaced sysctl value\n\nWhen writing to sysctls, proc_sys_call_handler() guarantees that the\nbuffer passed to proc handlers is NUL-terminated. If\nbpf_…","severity":"medium","vendor":"Linux","product":"Linux","affected":["Linux >= 32927393dc1ccd60fb2bdc05b9e8e88753761469 < bfcee1f79aaefa90679ad47690107fb7682724ec","Linux >= 32927393dc1ccd60fb2bdc05b9e8e88753761469 < c73e4a04eedc677fe91a736d7a5db45100adba5e","Linux >= 32927393dc1ccd60fb2bdc05b9e8e88753761469 < 36d3e9f62dc2beb9299d3bb6f589cb9e07f773fe","Linux >= 32927393dc1ccd60fb2bdc05b9e8e88753761469 < 31377675c3d75603d957c08e338a9ac27e9f6cd5","Linux >= 32927393dc1ccd60fb2bdc05b9e8e88753761469 < 76c14b10f50eb0afcc76e244562fa2d8c661e224","Linux >= 32927393dc1ccd60fb2bdc05b9e8e88753761469 < 3b2814dd842a565fcf9cc370156e1ba9eae16239","Linux >= 32927393dc1ccd60fb2bdc05b9e8e88753761469 < a66e3b5bacf38d6ab29fa05a9754f7a114485605","Linux 5.8"],"published":"2026-09-24","updated":"2026-10-03","sourceUpdated":"2026-10-03T11:17:54.123","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-97420","references":[{"url":"https://git.kernel.org/stable/c/31377675c3d75603d957c08e338a9ac27e9f6cd5","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/36d3e9f62dc2beb9299d3bb6f589cb9e07f773fe","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/3b2814dd842a565fcf9cc370156e1ba9eae16239","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/76c14b10f50eb0afcc76e244562fa2d8c661e224","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/a66e3b5bacf38d6ab29fa05a9754f7a114485605","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/bfcee1f79aaefa90679ad47690107fb7682724ec","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/c73e4a04eedc677fe91a736d7a5db45100adba5e","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-97420.json"},{"url":"https://access.redhat.com/security/cve/CVE-2026-97420"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2540519"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-97420"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-97420"},{"url":"https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-97420.mbox"}],"tags":["nvd","cve.org","csaf","vex","red-hat"],"epss":0.00173,"epssPercentile":0.06643,"ingestedAt":"2026-09-24T16:47:15.884Z","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-125"],"slug":"CVE-2026-97420","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nbpf: NUL-terminate replaced sysctl value\n\nWhen writing to sysctls, proc_sys_call_handler() guarantees that the\nbuffer passed to proc handlers is NUL-terminated. If\nbpf_sysctl_set_new_value() replaces the pending sysctl value, it can\nhand a replacement buffer directly to proc handlers. However, the\nhelper currently copies only buf_len bytes into that buffer without\nappending a NUL terminator, leaving downstream parsers vulnerable to\nout-of-bounds access.\n\nFix this by appending a '\\0' after the replaced value to restore the\nexpected sysctl semantics. Since the helper already rejects buf_len\ngreater than PAGE_SIZE - 1, there is always room for the extra byte.\n\nReproduced in a QEMU x86_64 guest booted with KASAN while exercising\nthe sysctl replacement path with a cgroup/sysctl BPF program. The\nreproducer targets `/proc/sys/net/core/flow_limit_cpu_bitmap`, fills\nthe original user write buffer with non-zero bytes, and overrides the\nsysctl value so the replacement buffer lacks a terminating NUL. Under\nthat setup, the pre-fix kernel reported:\n\n  BUG: KASAN: slab-out-of-bounds in strnchrnul+0x72/0x90\n  Read of size 1 at addr ffff88800de57000 by task repro_patch3/66\n  CPU: 0 UID: 0 PID: 66 Comm: repro_patch3 Not tainted 7.1.0-rc3-00269-g8370ca1f87cc #6 PREEMPT(lazy)\n  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014\n  Call Trace:\n   <TASK>\n   dump_stack_lvl+0x68/0xa0\n   print_report+0xcb/0x5e0\n   ? __virt_addr_valid+0x21d/0x3f0\n   ? strnchrnul+0x72/0x90\n   ? strnchrnul+0x72/0x90\n   kasan_report+0xca/0x100\n   ? strnchrnul+0x72/0x90\n   strnchrnul+0x72/0x90\n   bitmap_parse+0x37/0x2e0\n   flow_limit_cpu_sysctl+0xc6/0x840\n   ? __pfx_flow_limit_cpu_sysctl+0x10/0x10\n   ? __kvmalloc_node_noprof+0x5ba/0x870\n   proc_sys_call_handler+0x31d/0x480\n   ? __pfx_proc_sys_call_handler+0x10/0x10\n   ? selinux_file_permission+0x39f/0x500\n   ? lock_is_held_type+0x9e/0x120\n   vfs_write+0x98e/0x1000\n   ...\n   </TASK>\n  The buggy address is located 0 bytes to the right of\n  allocated 4096-byte region [ffff88800de56000, ffff88800de57000)\nWith this fix applied, rerunning the same sysctl-targeted path yields\nno corresponding KASAN reports.\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 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 2026-10-17 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-97420.json)","depth":"sunlit","depthScore":30,"depthScoreParts":{"impact":30.3,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[{"seq":224276,"id":"CVE-2026-97420","ts":1792325070503,"field":"cvss","old":null,"new":"5.5"},{"seq":224275,"id":"CVE-2026-97420","ts":1792325070503,"field":"severity","old":"none","new":"medium"}]}