{"id":"CVE-2025-21857","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-\u003eactions 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-\u003eactions 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]","modified":"2026-04-16T04:30:36.051749139Z","published":"2025-03-12T09:42:10.622Z","related":["ALSA-2025:20095","SUSE-SU-2025:01919-1","SUSE-SU-2025:01951-1","SUSE-SU-2025:01967-1","SUSE-SU-2025:1177-1","SUSE-SU-2025:1178-1","SUSE-SU-2025:1180-1","SUSE-SU-2025:20190-1","SUSE-SU-2025:20192-1","SUSE-SU-2025:20260-1","SUSE-SU-2025:20270-1","USN-7521-2"],"database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/21xxx/CVE-2025-21857.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/071ed42cff4fcdd89025d966d48eabef59913bf2"},{"type":"WEB","url":"https://git.kernel.org/stable/c/3c74b5787caf59bb1e9c5fe0a360643a71eb1e8a"},{"type":"WEB","url":"https://git.kernel.org/stable/c/3e4c56cf41876ef2a82f0877fe2a67648f8632b8"},{"type":"WEB","url":"https://git.kernel.org/stable/c/de4b679aa3b4da7ec34f639df068b914f20e3c3c"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/21xxx/CVE-2025-21857.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2025-21857"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"80cd22c35c9001fe72bf614d29439de41933deca"},{"fixed":"de4b679aa3b4da7ec34f639df068b914f20e3c3c"},{"fixed":"3e4c56cf41876ef2a82f0877fe2a67648f8632b8"},{"fixed":"3c74b5787caf59bb1e9c5fe0a360643a71eb1e8a"},{"fixed":"071ed42cff4fcdd89025d966d48eabef59913bf2"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2025-21857.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H"}]}