{
  "schema_version": "1.6.1",
  "id": "RPI-CVE-2025-21857",
  "modified": "2026-10-07T17:22:01Z",
  "upstream": [
    "CVE-2025-21857"
  ],
  "published": "2025-03-12T09:43:14Z",
  "summary": "net/sched: cls_api: fix error handling causing NULL dereference",
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: cls_api: fix error handling causing NULL dereference\n\ntcf_exts_miss_cookie_base_alloc() calls xa_alloc_cyclic() which can\nreturn 1 if the allocation succeeded after wrapping. This was treated as\nan error, with value 1 returned to caller tcf_exts_init_ex() which sets\nexts->actions to NULL and returns 1 to caller fl_change().\n\nfl_change() treats err == 1 as success, calling tcf_exts_validate_ex()\nwhich calls tcf_action_init() with exts->actions as argument, where it\nis dereferenced.\n\nExample trace:\n\nBUG: kernel NULL pointer dereference, address: 0000000000000000\nCPU: 114 PID: 16151 Comm: handler114 Kdump: loaded Not tainted 5.14.0-503.16.1.el9_5.x86_64 #1\nRIP: 0010:tcf_action_init+0x1f8/0x2c0\nCall Trace:\n tcf_action_init+0x1f8/0x2c0\n tcf_exts_validate_ex+0x175/0x190\n fl_change+0x537/0x1120 [cls_flower]",
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  "references": [
    {
      "type": "ADVISORY",
      "url": "https://www.cve.org/CVERecord?id=CVE-2025-21857"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/de4b679aa3b4da7ec34f639df068b914f20e3c3c"
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      "url": "https://git.kernel.org/stable/c/3e4c56cf41876ef2a82f0877fe2a67648f8632b8"
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      "url": "https://git.kernel.org/stable/c/3c74b5787caf59bb1e9c5fe0a360643a71eb1e8a"
    },
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    }
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    "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git",
    "upstream_modified": "2026-05-12T04:54:46Z"
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}