CVE-2026-97420 - Vulnerability Details

Vendors	Products
Linux Subscribe	Linux Kernel Subscribe

Link	Providers
https://git.kernel.org/stable/c/3b2814dd842a565fcf9cc370156e1ba9eae16239
https://git.kernel.org/stable/c/76c14b10f50eb0afcc76e244562fa2d8c661e224
https://git.kernel.org/stable/c/a66e3b5bacf38d6ab29fa05a9754f7a114485605

Type	Values Removed	Values Added
Description		In the Linux kernel, the following vulnerability has been resolved: bpf: NUL-terminate replaced sysctl value When writing to sysctls, proc_sys_call_handler() guarantees that the buffer passed to proc handlers is NUL-terminated. If bpf_sysctl_set_new_value() replaces the pending sysctl value, it can hand a replacement buffer directly to proc handlers. However, the helper currently copies only buf_len bytes into that buffer without appending a NUL terminator, leaving downstream parsers vulnerable to out-of-bounds access. Fix this by appending a '\0' after the replaced value to restore the expected sysctl semantics. Since the helper already rejects buf_len greater than PAGE_SIZE - 1, there is always room for the extra byte. Reproduced in a QEMU x86_64 guest booted with KASAN while exercising the sysctl replacement path with a cgroup/sysctl BPF program. The reproducer targets `/proc/sys/net/core/flow_limit_cpu_bitmap`, fills the original user write buffer with non-zero bytes, and overrides the sysctl value so the replacement buffer lacks a terminating NUL. Under that setup, the pre-fix kernel reported: BUG: KASAN: slab-out-of-bounds in strnchrnul+0x72/0x90 Read of size 1 at addr ffff88800de57000 by task repro_patch3/66 CPU: 0 UID: 0 PID: 66 Comm: repro_patch3 Not tainted 7.1.0-rc3-00269-g8370ca1f87cc #6 PREEMPT(lazy) Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014 Call Trace: <TASK> dump_stack_lvl+0x68/0xa0 print_report+0xcb/0x5e0 ? __virt_addr_valid+0x21d/0x3f0 ? strnchrnul+0x72/0x90 ? strnchrnul+0x72/0x90 kasan_report+0xca/0x100 ? strnchrnul+0x72/0x90 strnchrnul+0x72/0x90 bitmap_parse+0x37/0x2e0 flow_limit_cpu_sysctl+0xc6/0x840 ? __pfx_flow_limit_cpu_sysctl+0x10/0x10 ? __kvmalloc_node_noprof+0x5ba/0x870 proc_sys_call_handler+0x31d/0x480 ? __pfx_proc_sys_call_handler+0x10/0x10 ? selinux_file_permission+0x39f/0x500 ? lock_is_held_type+0x9e/0x120 vfs_write+0x98e/0x1000 ... </TASK> The buggy address is located 0 bytes to the right of allocated 4096-byte region [ffff88800de56000, ffff88800de57000) With this fix applied, rerunning the same sysctl-targeted path yields no corresponding KASAN reports.
Title		bpf: NUL-terminate replaced sysctl value
First Time appeared		Linux Linux linux Kernel
CPEs		cpe:2.3:o:linux:linux_kernel::::::::
Vendors & Products		Linux Linux linux Kernel
References		https://git.kernel.org/stable/c/3b2814dd842a565fcf9cc370156e1ba9eae16239 https://git.kernel.org/stable/c/76c14b10f50eb0afcc76e244562fa2d8c661e224 https://git.kernel.org/stable/c/a66e3b5bacf38d6ab29fa05a9754f7a114485605

{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-97420", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-24T14:53:16.868Z", "datePublished": "2026-09-24T16:03:30.084Z", "dateUpdated": "2026-09-24T16:03:30.084Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-09-24T16:03:30.084Z"}, "descriptions": [{"lang": "en", "value": "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_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."}], "affected": [{"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["kernel/bpf/cgroup.c"], "versions": [{"version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2", "lessThan": "76c14b10f50eb0afcc76e244562fa2d8c661e224", "status": "affected", "versionType": "git"}, {"version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2", "lessThan": "3b2814dd842a565fcf9cc370156e1ba9eae16239", "status": "affected", "versionType": "git"}, {"version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2", "lessThan": "a66e3b5bacf38d6ab29fa05a9754f7a114485605", "status": "affected", "versionType": "git"}, {"version": "0", "lessThan": "6.12.111", "status": "affected", "versionType": "semver"}, {"version": "0", "lessThan": "6.18.53", "status": "affected", "versionType": "semver"}]}, {"product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["kernel/bpf/cgroup.c"], "versions": [{"version": "6.12.111", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.18.53", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver"}, {"version": "7.2", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix"}]}], "cpeApplicability": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionEndExcluding": "6.12.111"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionEndExcluding": "6.18.53"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionEndExcluding": "7.2"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/76c14b10f50eb0afcc76e244562fa2d8c661e224"}, {"url": "https://git.kernel.org/stable/c/3b2814dd842a565fcf9cc370156e1ba9eae16239"}, {"url": "https://git.kernel.org/stable/c/a66e3b5bacf38d6ab29fa05a9754f7a114485605"}], "title": "bpf: NUL-terminate replaced sysctl value", "x_generator": {"engine": "bippy-1.2.0"}}}}

{"affected": [{"affectedData": [{"defaultStatus": "unaffected", "product": "Linux", "programFiles": ["kernel/bpf/cgroup.c"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"lessThan": "76c14b10f50eb0afcc76e244562fa2d8c661e224", "status": "affected", "version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2", "versionType": "git"}, {"lessThan": "3b2814dd842a565fcf9cc370156e1ba9eae16239", "status": "affected", "version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2", "versionType": "git"}, {"lessThan": "a66e3b5bacf38d6ab29fa05a9754f7a114485605", "status": "affected", "version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2", "versionType": "git"}, {"lessThan": "6.12.111", "status": "affected", "version": "0", "versionType": "semver"}, {"lessThan": "6.18.53", "status": "affected", "version": "0", "versionType": "semver"}]}, {"defaultStatus": "affected", "product": "Linux", "programFiles": ["kernel/bpf/cgroup.c"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"lessThanOrEqual": "6.12.*", "status": "unaffected", "version": "6.12.111", "versionType": "semver"}, {"lessThanOrEqual": "6.18.*", "status": "unaffected", "version": "6.18.53", "versionType": "semver"}, {"lessThanOrEqual": "*", "status": "unaffected", "version": "7.2", "versionType": "original_commit_for_fix"}]}], "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}], "cveTags": [], "descriptions": [{"lang": "en", "value": "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_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."}], "id": "CVE-2026-97420", "lastModified": "2026-09-24T17:17:19.853", "metrics": {}, "published": "2026-09-24T17:17:19.853", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/3b2814dd842a565fcf9cc370156e1ba9eae16239"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/76c14b10f50eb0afcc76e244562fa2d8c661e224"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/a66e3b5bacf38d6ab29fa05a9754f7a114485605"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Received"}

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