{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2023-53490","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","state":"PUBLISHED","assignerShortName":"Linux","dateReserved":"2025-10-01T11:39:39.403Z","datePublished":"2025-10-01T11:45:42.182Z","dateUpdated":"2026-08-05T09:14:22.176Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-08-05T09:14:22.176Z"},"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nmptcp: fix disconnect vs accept race\n\nDespite commit 0ad529d9fd2b (\"mptcp: fix possible divide by zero in\nrecvmsg()\"), the mptcp protocol is still prone to a race between\ndisconnect() (or shutdown) and accept.\n\nThe root cause is that the mentioned commit checks the msk-level\nflag, but mptcp_stream_accept() does acquire the msk-level lock,\nas it can rely directly on the first subflow lock.\n\nAs reported by Christoph than can lead to a race where an msk\nsocket is accepted after that mptcp_subflow_queue_clean() releases\nthe listener socket lock and just before it takes destructive\nactions leading to the following splat:\n\nBUG: kernel NULL pointer dereference, address: 0000000000000012\nPGD 5a4ca067 P4D 5a4ca067 PUD 37d4c067 PMD 0\nOops: 0000 [#1] PREEMPT SMP\nCPU: 2 PID: 10955 Comm: syz-executor.5 Not tainted 6.5.0-rc1-gdc7b257ee5dd #37\nHardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.11.0-2.el7 04/01/2014\nRIP: 0010:mptcp_stream_accept+0x1ee/0x2f0 include/net/inet_sock.h:330\nCode: 0a 09 00 48 8b 1b 4c 39 e3 74 07 e8 bc 7c 7f fe eb a1 e8 b5 7c 7f fe 4c 8b 6c 24 08 eb 05 e8 a9 7c 7f fe 49 8b 85 d8 09 00 00 <0f> b6 40 12 88 44 24 07 0f b6 6c 24 07 bf 07 00 00 00 89 ee e8 89\nRSP: 0018:ffffc90000d07dc0 EFLAGS: 00010293\nRAX: 0000000000000000 RBX: ffff888037e8d020 RCX: ffff88803b093300\nRDX: 0000000000000000 RSI: ffffffff833822c5 RDI: ffffffff8333896a\nRBP: 0000607f82031520 R08: ffff88803b093300 R09: 0000000000000000\nR10: 0000000000000000 R11: 0000000000003e83 R12: ffff888037e8d020\nR13: ffff888037e8c680 R14: ffff888009af7900 R15: ffff888009af6880\nFS:  00007fc26d708640(0000) GS:ffff88807dd00000(0000) knlGS:0000000000000000\nCS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033\nCR2: 0000000000000012 CR3: 0000000066bc5001 CR4: 0000000000370ee0\nDR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000\nDR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400\nCall Trace:\n <TASK>\n do_accept+0x1ae/0x260 net/socket.c:1872\n __sys_accept4+0x9b/0x110 net/socket.c:1913\n __do_sys_accept4 net/socket.c:1954 [inline]\n __se_sys_accept4 net/socket.c:1951 [inline]\n __x64_sys_accept4+0x20/0x30 net/socket.c:1951\n do_syscall_x64 arch/x86/entry/common.c:50 [inline]\n do_syscall_64+0x47/0xa0 arch/x86/entry/common.c:80\n entry_SYSCALL_64_after_hwframe+0x6e/0xd8\n\nAddress the issue by temporary removing the pending request socket\nfrom the accept queue, so that racing accept() can't touch them.\n\nAfter depleting the msk - the ssk still exists, as plain TCP sockets,\nre-insert them into the accept queue, so that later inet_csk_listen_stop()\nwill complete the tcp socket disposal."}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7.8,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:L - The race is between two local syscalls on the same MPTCP listening socket — `accept()` versus `close()`/`connect(AF_UNSPEC)`/shutdown — driven from the local process; a remote peer only supplies the pending connections and cannot itself schedule the disconnect.\nAC:L - The attacker controls both sides of the race with its own threads and can retry indefinitely over loopback, widening the window by queueing many unaccepted MPTCP connections; syzkaller reproduced it, so no attacker-uncontrollable precondition exists.\nPR:L - Only an unprivileged local user account is needed — creating `IPPROTO_MPTCP` sockets and calling listen/accept/close involves no capability check, and `net.mptcp.enabled` defaults to 1 including in a user-namespace-created netns (`unshare -Urn`).\nUI:N - The attacking process performs every step itself — creating the listener, generating connections, and racing accept against disconnect; no victim action is involved.\nS:U - The corrupted objects (`struct mptcp_sock`, subflow context) and the impact remain within the kernel's own security authority, with no crossing of a VM, IOMMU, or sandbox boundary.\nC:H - `mptcp_accept()` retains `subflow->conn` without a reference while `mptcp_subflow_queue_clean()` destroys and frees the msk and `kfree_rcu()`s the subflow context, so the accept path reads freed heap memory (`msk->first`, `msk->conn_list`, `subflow->tcp_sock`) — a use-after-free read that can be groomed into disclosing reclaimed kernel data.\nI:H - The racing `accept()` writes into the freed msk — `lock_sock()` on the freed socket lock, `sock_graft()` setting `sk_socket`/`sk_wq`, and `msk->in_accept_queue = 0` — giving controlled writes into reclaimed slab memory that are leverageable for control-flow hijack via heap spraying.\nA:H - The bug reproduces as an immediate kernel NULL-pointer dereference oops in `mptcp_stream_accept()` (`CR2=0000000000000012`), and the underlying use-after-free causes further panics; any local user can trigger it repeatedly to take down the system."}]}],"affected":[{"product":"Linux","vendor":"Linux","defaultStatus":"unaffected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/mptcp/protocol.h","net/mptcp/subflow.c"],"versions":[{"version":"b45d8f5375eda3ddc89fe529b58bb643917bd87b","lessThan":"ded9f5551ce5cafa3c41c794428c27a0d0a00542","status":"affected","versionType":"git"},{"version":"2a6a870e44dd88f1a6a2893c65ef756a9edfb4c7","lessThan":"b2b4c84eb7149f34c0f25f17042d095ba5357d68","status":"affected","versionType":"git"},{"version":"2a6a870e44dd88f1a6a2893c65ef756a9edfb4c7","lessThan":"511b90e39250135a7f900f1c3afbce25543018a2","status":"affected","versionType":"git"},{"version":"64b66601308dae6105fbde964a339462a29c2a73","status":"affected","versionType":"git"},{"version":"6.1.27","lessThan":"6.1.46","status":"affected","versionType":"semver"},{"version":"6.2.13","lessThan":"6.3","status":"affected","versionType":"semver"}]},{"product":"Linux","vendor":"Linux","defaultStatus":"affected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/mptcp/protocol.h","net/mptcp/subflow.c"],"versions":[{"version":"6.3","status":"affected"},{"version":"0","lessThan":"6.3","status":"unaffected","versionType":"semver"},{"version":"6.1.46","lessThanOrEqual":"6.1.*","status":"unaffected","versionType":"semver"},{"version":"6.4.11","lessThanOrEqual":"6.4.*","status":"unaffected","versionType":"semver"},{"version":"6.5","lessThanOrEqual":"*","status":"unaffected","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.1.27","versionEndExcluding":"6.1.46"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.3","versionEndExcluding":"6.4.11"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.3","versionEndExcluding":"6.5"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.2.13"}]}]}],"references":[{"url":"https://git.kernel.org/stable/c/ded9f5551ce5cafa3c41c794428c27a0d0a00542"},{"url":"https://git.kernel.org/stable/c/b2b4c84eb7149f34c0f25f17042d095ba5357d68"},{"url":"https://git.kernel.org/stable/c/511b90e39250135a7f900f1c3afbce25543018a2"}],"title":"mptcp: fix disconnect vs accept race","x_generator":{"engine":"bippy-1.2.0"}}}}