{
  "affected": [
    {
      "ecosystem_specific": {
        "urgency": "not yet assigned"
      },
      "package": {
        "ecosystem": "Debian:12",
        "name": "linux"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "ecosystem_specific": {
        "urgency": "not yet assigned"
      },
      "package": {
        "ecosystem": "Debian:13",
        "name": "linux"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "ecosystem_specific": {
        "urgency": "not yet assigned"
      },
      "package": {
        "ecosystem": "Debian:14",
        "name": "linux"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "7.2.6-1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "details": "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:    \u003cTASK\u003e    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    ...    \u003c/TASK\u003e   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.",
  "id": "DEBIAN-CVE-2026-97420",
  "modified": "2026-09-26T08:47:42.666043918Z",
  "published": "2026-09-24T17:17:19.853Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://security-tracker.debian.org/tracker/CVE-2026-97420"
    }
  ],
  "upstream": [
    "CVE-2026-97420"
  ]
}