{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2021-47448", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2024-05-21T14:58:30.832Z", "datePublished": "2024-05-22T06:19:40.141Z", "dateUpdated": "2026-08-05T08:47:51.948Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T08:47:51.948Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nmptcp: fix possible stall on recvmsg()\n\nrecvmsg() can enter an infinite loop if the caller provides the\nMSG_WAITALL, the data present in the receive queue is not sufficient to\nfulfill the request, and no more data is received by the peer.\n\nWhen the above happens, mptcp_wait_data() will always return with\nno wait, as the MPTCP_DATA_READY flag checked by such function is\nset and never cleared in such code path.\n\nLeveraging the above syzbot was able to trigger an RCU stall:\n\nrcu: INFO: rcu_preempt self-detected stall on CPU\nrcu: 0-...!: (10499 ticks this GP) idle=0af/1/0x4000000000000000 softirq=10678/10678 fqs=1\n (t=10500 jiffies g=13089 q=109)\nrcu: rcu_preempt kthread starved for 10497 jiffies! g13089 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=1\nrcu: Unless rcu_preempt kthread gets sufficient CPU time, OOM is now expected behavior.\nrcu: RCU grace-period kthread stack dump:\ntask:rcu_preempt state:R running task stack:28696 pid: 14 ppid: 2 flags:0x00004000\nCall Trace:\n context_switch kernel/sched/core.c:4955 [inline]\n __schedule+0x940/0x26f0 kernel/sched/core.c:6236\n schedule+0xd3/0x270 kernel/sched/core.c:6315\n schedule_timeout+0x14a/0x2a0 kernel/time/timer.c:1881\n rcu_gp_fqs_loop+0x186/0x810 kernel/rcu/tree.c:1955\n rcu_gp_kthread+0x1de/0x320 kernel/rcu/tree.c:2128\n kthread+0x405/0x4f0 kernel/kthread.c:327\n ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295\nrcu: Stack dump where RCU GP kthread last ran:\nSending NMI from CPU 0 to CPUs 1:\nNMI backtrace for cpu 1\nCPU: 1 PID: 8510 Comm: syz-executor827 Not tainted 5.15.0-rc2-next-20210920-syzkaller #0\nHardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011\nRIP: 0010:bytes_is_nonzero mm/kasan/generic.c:84 [inline]\nRIP: 0010:memory_is_nonzero mm/kasan/generic.c:102 [inline]\nRIP: 0010:memory_is_poisoned_n mm/kasan/generic.c:128 [inline]\nRIP: 0010:memory_is_poisoned mm/kasan/generic.c:159 [inline]\nRIP: 0010:check_region_inline mm/kasan/generic.c:180 [inline]\nRIP: 0010:kasan_check_range+0xc8/0x180 mm/kasan/generic.c:189\nCode: 38 00 74 ed 48 8d 50 08 eb 09 48 83 c0 01 48 39 d0 74 7a 80 38 00 74 f2 48 89 c2 b8 01 00 00 00 48 85 d2 75 56 5b 5d 41 5c c3 <48> 85 d2 74 5e 48 01 ea eb 09 48 83 c0 01 48 39 d0 74 50 80 38 00\nRSP: 0018:ffffc9000cd676c8 EFLAGS: 00000283\nRAX: ffffed100e9a110e RBX: ffffed100e9a110f RCX: ffffffff88ea062a\nRDX: 0000000000000001 RSI: 0000000000000008 RDI: ffff888074d08870\nRBP: ffffed100e9a110e R08: 0000000000000001 R09: ffff888074d08877\nR10: ffffed100e9a110e R11: 0000000000000000 R12: ffff888074d08000\nR13: ffff888074d08000 R14: ffff888074d08088 R15: ffff888074d08000\nFS: 0000555556d8e300(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000\nS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033\nCR2: 0000000020000180 CR3: 0000000068909000 CR4: 00000000001506e0\nDR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000\nDR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400\nCall Trace:\n instrument_atomic_read_write include/linux/instrumented.h:101 [inline]\n test_and_clear_bit include/asm-generic/bitops/instrumented-atomic.h:83 [inline]\n mptcp_release_cb+0x14a/0x210 net/mptcp/protocol.c:3016\n release_sock+0xb4/0x1b0 net/core/sock.c:3204\n mptcp_wait_data net/mptcp/protocol.c:1770 [inline]\n mptcp_recvmsg+0xfd1/0x27b0 net/mptcp/protocol.c:2080\n inet6_recvmsg+0x11b/0x5e0 net/ipv6/af_inet6.c:659\n sock_recvmsg_nosec net/socket.c:944 [inline]\n ____sys_recvmsg+0x527/0x600 net/socket.c:2626\n ___sys_recvmsg+0x127/0x200 net/socket.c:2670\n do_recvmmsg+0x24d/0x6d0 net/socket.c:2764\n __sys_recvmmsg net/socket.c:2843 [inline]\n __do_sys_recvmmsg net/socket.c:2866 [inline]\n __se_sys_recvmmsg net/socket.c:2859 [inline]\n __x64_sys_recvmmsg+0x20b/0x260 net/socket.c:2859\n do_syscall_x64 arch/x86/entry/common.c:50 [inline]\n do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80\n entry_SYSCALL_64_after_hwframe+0x44/0xae\nRIP: 0033:0x7fc200d2\n---truncated---" } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "baseScore": 7.5, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:N - MPTCP is a network transport, and a remote peer of an MPTCP service that calls recvmsg with MSG_WAITALL can send partial data then stop, leaving MPTCP_DATA_READY set so the victim’s receive path busy-loops. This is reachable through ordinary MPTCP connection handling, not only a local syscall.\nAC:L - The attacker fully controls how much data is sent and when sending stops; no race, special memory layout, or other condition outside attacker influence is required. syzbot reproduced the stall reliably.\nPR:N - No local account or capability is needed: an unauthenticated peer can connect to an exposed MPTCP listener and trigger the path before any application authentication. Creating IPPROTO_MPTCP sockets itself has no privilege gate and MPTCP is enabled by default when configured.\nUI:N - Exploitation requires only the vulnerable service’s normal blocking receive; no additional interactive user action is needed.\nS:U - The impact is a kernel soft lockup/RCU stall on the same host. It does not cross a VM, IOMMU, or other security-authority boundary.\nC:N - This is a pure control-flow hang from a stuck wait flag; there is no memory corruption or information-disclosure primitive.\nI:N - No unauthorized write, data modification, or control-flow hijacking occurs; the failure mode is only an infinite receive/wait loop.\nA:H - The busy loop prevents proper sleeping in mptcp_wait_data and was shown to cause RCU stalls and CPU starvation, which is a high availability impact; repeated connections can amplify the DoS." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "net/mptcp/protocol.c" ], "versions": [ { "version": "7a6a6cbc3e592e339ad23e4e8ede9a3f6160bda8", "lessThan": "1a4554e94f0deff9fc1dc5addf93fa579cc29711", "status": "affected", "versionType": "git" }, { "version": "7a6a6cbc3e592e339ad23e4e8ede9a3f6160bda8", "lessThan": "612f71d7328c14369924384ad2170aae2a6abd92", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "net/mptcp/protocol.c" ], "versions": [ { "version": "5.6", "status": "affected" }, { "version": "0", "lessThan": "5.6", "status": "unaffected", "versionType": "semver" }, { "version": "5.14.14", "lessThanOrEqual": "5.14.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.15", "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": "5.6", "versionEndExcluding": "5.14.14" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.6", "versionEndExcluding": "5.15" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/1a4554e94f0deff9fc1dc5addf93fa579cc29711" }, { "url": "https://git.kernel.org/stable/c/612f71d7328c14369924384ad2170aae2a6abd92" } ], "title": "mptcp: fix possible stall on recvmsg()", "x_generator": { "engine": "bippy-1.2.0" } }, "adp": [ { "providerMetadata": { "orgId": "af854a3a-2127-422b-91ae-364da2661108", "shortName": "CVE", "dateUpdated": "2024-08-04T05:39:59.611Z" }, "title": "CVE Program Container", "references": [ { "url": "https://git.kernel.org/stable/c/1a4554e94f0deff9fc1dc5addf93fa579cc29711", "tags": [ "x_transferred" ] }, { "url": "https://git.kernel.org/stable/c/612f71d7328c14369924384ad2170aae2a6abd92", "tags": [ "x_transferred" ] } ] }, { "metrics": [ { "other": { "type": "ssvc", "content": { "id": "CVE-2021-47448", "role": "CISA Coordinator", "options": [ { "Exploitation": "none" }, { "Automatable": "no" }, { "Technical Impact": "partial" } ], "version": "2.0.3", "timestamp": "2024-09-10T15:36:18.098656Z" } } } ], "title": "CISA ADP Vulnrichment", "providerMetadata": { "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2024-09-11T17:33:26.764Z" } } ] } }