{"cve":"CVE-2025-40271","nvd":{"published":"2025-12-06T22:15:54.737","modified":"2026-10-15T19:10:00.173","status":"Deferred","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nfs/proc: fix uaf in proc_readdir_de()\n\nPde is erased from subdir rbtree through rb_erase(), but not set the node\nto EMPTY, which may result in uaf access.  We should use RB_CLEAR_NODE()\nset the erased node to EMPTY, then pde_subdir_next() will return NULL to\navoid uaf access.\n\nWe found an uaf issue while using stress-ng testing, need to run testcase\ngetdent and tun in the same time.  The steps of the issue is as follows:\n\n1) use getdent to traverse dir /proc/pid/net/dev_snmp6/, and current\n   pde is tun3;\n\n2) in the [time windows] unregister netdevice tun3 and tun2, and erase\n   them from rbtree.  erase tun3 first, and then erase tun2.  the\n   pde(tun2) will be released to slab;\n\n3) continue to getdent process, then pde_subdir_next() will return\n   pde(tun2) which is released, it will case uaf access.\n\nCPU 0                                      |    CPU 1\n-------------------------------------------------------------------------\ntraverse dir /proc/pid/net/dev_snmp6/      |   unregister_netdevice(tun->dev)   //tun3 tun2\nsys_getdents64()                           |\n  iterate_dir()                            |\n    proc_readdir()                         |\n      proc_readdir_de()                    |     snmp6_unregister_dev()\n        pde_get(de);                       |       proc_remove()\n        read_unlock(&proc_subdir_lock);    |         remove_proc_subtree()\n                                           |           write_lock(&proc_subdir_lock);\n        [time window]                      |           rb_erase(&root->subdir_node, &parent->subdir);\n                                           |           write_unlock(&proc_subdir_lock);\n        read_lock(&proc_subdir_lock);      |\n        next = pde_subdir_next(de);        |\n        pde_put(de);                       |\n        de = next;    //UAF                |\n\nrbtree of dev_snmp6\n                        |\n                    pde(tun3)\n                     /    \\\n                  NULL  pde(tun2)","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","score":7.8},"cwes":[],"references":["https://git.kernel.org/stable/c/03de7ff197a3d0e17d0d5c58fdac99a63cba8110","https://git.kernel.org/stable/c/1d1596d68a6f11d28f677eedf6cf5b17dbfeb491","https://git.kernel.org/stable/c/4cba73c4c89219beef7685a47374bf88b1022369","https://git.kernel.org/stable/c/623bb26127fb581a741e880e1e1a47d79aecb6f8","https://git.kernel.org/stable/c/67272c11f379d9aa5e0f6b16286b9d89b3f76046"],"products":[],"source":"nvd","synced_at":"2026-10-19T22:16:40.427100871+00:00"},"epss":{"cve":"CVE-2025-40271","score":0.00455,"percentile":0.39255,"date":"2026-10-25"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}