{"id":"CVE-2025-21792","summary":"ax25: Fix refcount leak caused by setting SO_BINDTODEVICE sockopt","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nax25: Fix refcount leak caused by setting SO_BINDTODEVICE sockopt\n\nIf an AX25 device is bound to a socket by setting the SO_BINDTODEVICE\nsocket option, a refcount leak will occur in ax25_release().\n\nCommit 9fd75b66b8f6 (\"ax25: Fix refcount leaks caused by ax25_cb_del()\")\nadded decrement of device refcounts in ax25_release(). In order for that\nto work correctly the refcounts must already be incremented when the\ndevice is bound to the socket. An AX25 device can be bound to a socket\nby either calling ax25_bind() or setting SO_BINDTODEVICE socket option.\nIn both cases the refcounts should be incremented, but in fact it is done\nonly in ax25_bind().\n\nThis bug leads to the following issue reported by Syzkaller:\n\n================================================================\nrefcount_t: decrement hit 0; leaking memory.\nWARNING: CPU: 1 PID: 5932 at lib/refcount.c:31 refcount_warn_saturate+0x1ed/0x210 lib/refcount.c:31\nModules linked in:\nCPU: 1 UID: 0 PID: 5932 Comm: syz-executor424 Not tainted 6.13.0-rc4-syzkaller-00110-g4099a71718b0 #0\nHardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014\nRIP: 0010:refcount_warn_saturate+0x1ed/0x210 lib/refcount.c:31\nCall Trace:\n \u003cTASK\u003e\n __refcount_dec include/linux/refcount.h:336 [inline]\n refcount_dec include/linux/refcount.h:351 [inline]\n ref_tracker_free+0x710/0x820 lib/ref_tracker.c:236\n netdev_tracker_free include/linux/netdevice.h:4156 [inline]\n netdev_put include/linux/netdevice.h:4173 [inline]\n netdev_put include/linux/netdevice.h:4169 [inline]\n ax25_release+0x33f/0xa10 net/ax25/af_ax25.c:1069\n __sock_release+0xb0/0x270 net/socket.c:640\n sock_close+0x1c/0x30 net/socket.c:1408\n ...\n do_syscall_x64 arch/x86/entry/common.c:52 [inline]\n do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83\n entry_SYSCALL_64_after_hwframe+0x77/0x7f\n ...\n \u003c/TASK\u003e\n================================================================\n\nFix the implementation of ax25_setsockopt() by adding increment of\nrefcounts for the new device bound, and decrement of refcounts for\nthe old unbound device.","modified":"2026-03-20T12:41:10.593949Z","published":"2025-02-27T02:18:29.653Z","related":["SUSE-SU-2025:01614-1","SUSE-SU-2025:01707-1","SUSE-SU-2025:01919-1","SUSE-SU-2025:01951-1","SUSE-SU-2025:01964-1","SUSE-SU-2025:01967-1","SUSE-SU-2025:01972-1","SUSE-SU-2025:20343-1","SUSE-SU-2025:20344-1","SUSE-SU-2025:20354-1","SUSE-SU-2025:20355-1","USN-7521-2"],"database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/21xxx/CVE-2025-21792.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/470bda72fda0fcf54300466d70ce2de62f7835d2"},{"type":"WEB","url":"https://git.kernel.org/stable/c/90056ece99966182dc0e367f3fd2afab46ada847"},{"type":"WEB","url":"https://git.kernel.org/stable/c/94a0de224ed52eb2ecd4f4cb1b937b674c9fb955"},{"type":"WEB","url":"https://git.kernel.org/stable/c/b58f7ca86a7b8e480c06e30c5163c5d2f4e24023"},{"type":"WEB","url":"https://git.kernel.org/stable/c/bca0902e61731a75fc4860c8720168d9f1bae3b6"},{"type":"WEB","url":"https://lists.debian.org/debian-lts-announce/2025/03/msg00028.html"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/21xxx/CVE-2025-21792.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2025-21792"},{"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":"9fd75b66b8f68498454d685dc4ba13192ae069b0"},{"fixed":"90056ece99966182dc0e367f3fd2afab46ada847"},{"fixed":"94a0de224ed52eb2ecd4f4cb1b937b674c9fb955"},{"fixed":"b58f7ca86a7b8e480c06e30c5163c5d2f4e24023"},{"fixed":"470bda72fda0fcf54300466d70ce2de62f7835d2"},{"fixed":"bca0902e61731a75fc4860c8720168d9f1bae3b6"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"0"},{"last_affected":"c44a453ffe16eb08acdc6129ac4fa0192dbc0456"},{"last_affected":"de55a1338e6a48ff1e41ea8db1432496fbe2a62b"},{"last_affected":"9e1e088a57c23251f1cfe9601bbd90ade2ea73b9"},{"last_affected":"b20a5ab0f5fb175750c6bafd4cf12daccf00c738"},{"last_affected":"452ae92b99062d2f6a34324eaf705a3b7eac9f8b"},{"last_affected":"534156dd4ed768e30a43de0036f45dca7c54818f"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2025-21792.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"}]}