{"cve":"CVE-2023-53489","nvd":{"published":"2025-10-01T12:15:51.950","modified":"2026-06-17T06:45:27.387","status":"Analyzed","description":"In the Linux kernel, the following vulnerability has been resolved:\n\ntcp/udp: Fix memleaks of sk and zerocopy skbs with TX timestamp.\n\nsyzkaller reported [0] memory leaks of an UDP socket and ZEROCOPY\nskbs.  We can reproduce the problem with these sequences:\n\n  sk = socket(AF_INET, SOCK_DGRAM, 0)\n  sk.setsockopt(SOL_SOCKET, SO_TIMESTAMPING, SOF_TIMESTAMPING_TX_SOFTWARE)\n  sk.setsockopt(SOL_SOCKET, SO_ZEROCOPY, 1)\n  sk.sendto(b'', MSG_ZEROCOPY, ('127.0.0.1', 53))\n  sk.close()\n\nsendmsg() calls msg_zerocopy_alloc(), which allocates a skb, sets\nskb->cb->ubuf.refcnt to 1, and calls sock_hold().  Here, struct\nubuf_info_msgzc indirectly holds a refcnt of the socket.  When the\nskb is sent, __skb_tstamp_tx() clones it and puts the clone into\nthe socket's error queue with the TX timestamp.\n\nWhen the original skb is received locally, skb_copy_ubufs() calls\nskb_unclone(), and pskb_expand_head() increments skb->cb->ubuf.refcnt.\nThis additional count is decremented while freeing the skb, but struct\nubuf_info_msgzc still has a refcnt, so __msg_zerocopy_callback() is\nnot called.\n\nThe last refcnt is not released unless we retrieve the TX timestamped\nskb by recvmsg().  Since we clear the error queue in inet_sock_destruct()\nafter the socket's refcnt reaches 0, there is a circular dependency.\nIf we close() the socket holding such skbs, we never call sock_put()\nand leak the count, sk, and skb.\n\nTCP has the same problem, and commit e0c8bccd40fc (\"net: stream:\npurge sk_error_queue in sk_stream_kill_queues()\") tried to fix it\nby calling skb_queue_purge() during close().  However, there is a\nsmall chance that skb queued in a qdisc or device could be put\ninto the error queue after the skb_queue_purge() call.\n\nIn __skb_tstamp_tx(), the cloned skb should not have a reference\nto the ubuf to remove the circular dependency, but skb_clone() does\nnot call skb_copy_ubufs() for zerocopy skb.  So, we need to call\nskb_orphan_frags_rx() for the cloned skb to call skb_copy_ubufs().\n\n[0]:\nBUG: memory leak\nunreferenced object 0xffff88800c6d2d00 (size 1152):\n  comm \"syz-executor392\", pid 264, jiffies 4294785440 (age 13.044s)\n  hex dump (first 32 bytes):\n    00 00 00 00 00 00 00 00 cd af e8 81 00 00 00 00  ................\n    02 00 07 40 00 00 00 00 00 00 00 00 00 00 00 00  ...@............\n  backtrace:\n    [<0000000055636812>] sk_prot_alloc+0x64/0x2a0 net/core/sock.c:2024\n    [<0000000054d77b7a>] sk_alloc+0x3b/0x800 net/core/sock.c:2083\n    [<0000000066f3c7e0>] inet_create net/ipv4/af_inet.c:319 [inline]\n    [<0000000066f3c7e0>] inet_create+0x31e/0xe40 net/ipv4/af_inet.c:245\n    [<000000009b83af97>] __sock_create+0x2ab/0x550 net/socket.c:1515\n    [<00000000b9b11231>] sock_create net/socket.c:1566 [inline]\n    [<00000000b9b11231>] __sys_socket_create net/socket.c:1603 [inline]\n    [<00000000b9b11231>] __sys_socket_create net/socket.c:1588 [inline]\n    [<00000000b9b11231>] __sys_socket+0x138/0x250 net/socket.c:1636\n    [<000000004fb45142>] __do_sys_socket net/socket.c:1649 [inline]\n    [<000000004fb45142>] __se_sys_socket net/socket.c:1647 [inline]\n    [<000000004fb45142>] __x64_sys_socket+0x73/0xb0 net/socket.c:1647\n    [<0000000066999e0e>] do_syscall_x64 arch/x86/entry/common.c:50 [inline]\n    [<0000000066999e0e>] do_syscall_64+0x38/0x90 arch/x86/entry/common.c:80\n    [<0000000017f238c1>] entry_SYSCALL_64_after_hwframe+0x63/0xcd\n\nBUG: memory leak\nunreferenced object 0xffff888017633a00 (size 240):\n  comm \"syz-executor392\", pid 264, jiffies 4294785440 (age 13.044s)\n  hex dump (first 32 bytes):\n    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................\n    00 00 00 00 00 00 00 00 00 2d 6d 0c 80 88 ff ff  .........-m.....\n  backtrace:\n    [<000000002b1c4368>] __alloc_skb+0x229/0x320 net/core/skbuff.c:497\n    [<00000000143579a6>] alloc_skb include/linux/skbuff.h:1265 [inline]\n    [<00000000143579a6>] sock_omalloc+0xaa/0x190 net/core/sock.c:2596\n    [<00000000be626478>] msg_zerocopy_alloc net/core/skbuff.c:1294 [inline]\n    [<00000000be626478>]\n---truncated---","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","score":5.5},"cwes":["CWE-401"],"references":["https://git.kernel.org/stable/c/1f69c086b20e27763af28145981435423f088268","https://git.kernel.org/stable/c/230a5ed7d813fb516de81d23f09d7506753e41e9","https://git.kernel.org/stable/c/281072fb2a7294cde7acbf5375b879f40a8001b7","https://git.kernel.org/stable/c/30290f210ba7426ff7592fe2eb4114b1b5bad219","https://git.kernel.org/stable/c/426384dd4980040651536fef5feac4dcc4d7ee4e"],"products":["linux:linux_kernel"],"source":"nvd","synced_at":"2026-10-19T22:11:26.888974865+00:00"},"epss":{"cve":"CVE-2023-53489","score":0.00163,"percentile":0.05494,"date":"2026-10-31"},"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."]}