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CVE-2026-72166— net/9p: fix infinite loop in p9_client_rpc on fatal signal

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Linux kernel是美国Linux基金会开源的一个操作系统内核。 Linux kernel存在安全漏洞，该漏洞源于p9_client_rpc函数在处理P9_TFLUSH请求时对致命信号处理不当，清除TIF_SIGPENDING标志导致无限循环，可能导致拒绝服务。

AI Predicted 5.5 Difficulty: Easy EPSS 0.21% · P11

Possible ATT&CK Techniques 1 AI

T1496 · Resource Hijacking

Affected Version Matrix 18

VendorProduct Version RangeStatus
Linux Linux 91b8534fa8f5e01f249b1bf8df0a2540053549ad< 18a3427526e2141f80050f82c1d26b19a454707d affected
91b8534fa8f5e01f249b1bf8df0a2540053549ad< 378481cc60a937ef8ea4ef6e4f95f0dbc4e21414 affected
91b8534fa8f5e01f249b1bf8df0a2540053549ad< 4f621ae3a2d99b0bac50e8d66cbf7f68323c01e8 affected
91b8534fa8f5e01f249b1bf8df0a2540053549ad< f62a1f245a71680033260a6f6d74011cc3acb3cd affected
91b8534fa8f5e01f249b1bf8df0a2540053549ad< dc892cbb1e4341d427b1f940ebd6abd69bf8e479 affected
91b8534fa8f5e01f249b1bf8df0a2540053549ad< a8874c34c4a973f9922908a4b8be1d1278f01e42 affected
91b8534fa8f5e01f249b1bf8df0a2540053549ad< 823886a1b089b49bcd349bc8bd3417b7910cd1ac affected
91b8534fa8f5e01f249b1bf8df0a2540053549ad< 6b4f48728faa8bb514368f7eacda05565dea8696 affected
… +10 more rows
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I. Basic Information for CVE-2026-72166

Vulnerability Information
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Vulnerability Title
net/9p: fix infinite loop in p9_client_rpc on fatal signal
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: net/9p: fix infinite loop in p9_client_rpc on fatal signal When p9_client_rpc() is called with type P9_TFLUSH and the transport has no peer (e.g. fd transport backed by pipes with no 9p server), a fatal signal causes an infinite loop: again: err = io_wait_event_killable(req->wq, ...) /* SIGKILL wakes the task, returns -ERESTARTSYS */ if (err == -ERESTARTSYS && c->status == Connected && type == P9_TFLUSH) { sigpending = 1; clear_thread_flag(TIF_SIGPENDING); goto again; } clear_thread_flag() clears TIF_SIGPENDING before jumping back to io_wait_event_killable(). signal_pending_state() checks TIF_SIGPENDING, finds it zero, and the task goes to sleep again. The task can only wake on the next signal delivery that calls signal_wake_up() and sets TIF_SIGPENDING again. When that happens the loop repeats, clears TIF_SIGPENDING, and sleeps again indefinitely. This is triggered in practice by coredump_wait(): when a thread in a multi-threaded process causes a coredump (e.g. via SIGSYS from Syscall User Dispatch), coredump_wait() sends SIGKILL to all other threads and waits for them to call mm_release(). If one of those threads is blocked in p9_client_rpc() over an fd transport with no peer, it enters the P9_TFLUSH loop and never calls mm_release(), so coredump_wait() stalls forever: INFO: task syz.0.18:676 blocked for more than 143 seconds. Not tainted 6.12.77+ #1 task:syz.0.18 state:D stack:27600 pid:676 tgid:673 ppid:630 flags:0x00000004 Call Trace: <TASK> context_switch kernel/sched/core.c:5344 [inline] __schedule+0xcb4/0x5d50 kernel/sched/core.c:6724 __schedule_loop kernel/sched/core.c:6801 [inline] schedule+0xe5/0x350 kernel/sched/core.c:6816 schedule_timeout+0x253/0x290 kernel/time/timer.c:2593 do_wait_for_common kernel/sched/completion.c:95 [inline] __wait_for_common+0x409/0x600 kernel/sched/completion.c:116 wait_for_common kernel/sched/completion.c:127 [inline] wait_for_completion_state+0x1d/0x40 kernel/sched/completion.c:264 coredump_wait fs/coredump.c:448 [inline] do_coredump+0x854/0x4350 fs/coredump.c:629 get_signal+0x1425/0x2730 kernel/signal.c:2903 arch_do_signal_or_restart+0x81/0x880 arch/x86/kernel/signal.c:337 exit_to_user_mode_loop kernel/entry/common.c:111 [inline] exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline] __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline] syscall_exit_to_user_mode+0xf9/0x160 kernel/entry/common.c:218 do_syscall_64+0x102/0x220 arch/x86/entry/common.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f </TASK> Fix: check fatal_signal_pending() before clearing TIF_SIGPENDING in the P9_TFLUSH retry loop. At that point TIF_SIGPENDING is still set, so fatal_signal_pending() works correctly. If a fatal signal is pending, jump to recalc_sigpending to restore TIF_SIGPENDING and return -ERESTARTSYS to the caller. The same defect is present in stable kernels back to 5.4. On those kernels the infinite loop is broken earlier by a second SIGKILL from the parent process (e.g. kill_and_wait() retrying after a timeout), resulting in a zombie process and a shutdown delay rather than a permanent D-state hang, but the underlying flaw is the same. Found by Linux Verification Center (linuxtesting.org) with Syzkaller.
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会开源的一个操作系统内核。 Linux kernel存在安全漏洞，该漏洞源于p9_client_rpc函数在处理P9_TFLUSH请求时对致命信号处理不当，清除TIF_SIGPENDING标志导致无限循环，可能导致拒绝服务。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux 91b8534fa8f5e01f249b1bf8df0a2540053549ad ~ 18a3427526e2141f80050f82c1d26b19a454707d -
Linux Linux 2.6.28 -

II. Public POCs for CVE-2026-72166

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III. Intelligence Information for CVE-2026-72166

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Patches & Fixes for CVE-2026-72166 (8)

Same Patch Batch · Linux · 2026-08-15 · 845 CVEs total

CVE-2026-74475 10.0 CRITICAL vxlan: use neigh_ha_snapshot() in route_shortcircuit()
CVE-2026-74280 10.0 CRITICAL crypto: marvell/octeontx - fix DMA cleanup using wrong loop index
CVE-2026-74279 10.0 CRITICAL crypto: cavium/cpt - fix DMA cleanup using wrong loop index
CVE-2026-72408 10.0 CRITICAL geneve: gate GRO hint in geneve_gro_complete() on gs->gro_hint
CVE-2026-74309 10.0 CRITICAL vdpa/octeon_ep: fix IRQ-to-ring mapping in interrupt handler
CVE-2026-72421 10.0 CRITICAL ipv4: fib: Don't ignore error route in local/main tables.
CVE-2026-72407 10.0 CRITICAL geneve: validate inner network offset in geneve_gro_complete()
CVE-2026-72493 9.9 CRITICAL net: serialize netif_running() check in enqueue_to_backlog()
CVE-2026-72201 9.8 CRITICAL ntfs: validate index entries on reading
CVE-2026-72065 9.8 CRITICAL net: mana: Validate the packet length reported by the NIC
CVE-2026-72064 9.8 CRITICAL net: mana: Sync page pool RX frags for CPU
CVE-2026-74480 9.8 CRITICAL net: bridge: stop fast-leave after deleting a port group
CVE-2026-72191 9.8 CRITICAL ntfs3: validate split-point offset in indx_insert_into_buffer
CVE-2026-72192 9.8 CRITICAL ntfs3: bound to_move in indx_insert_into_root before hdr_insert_head
CVE-2026-74478 9.8 CRITICAL um: vector: fix use-after-free in vector_mmsg_rx()
CVE-2026-72194 9.8 CRITICAL fs/ntfs3: add depth limit to indx_find_buffer to prevent stack overflow
CVE-2026-74269 9.8 CRITICAL bnxt: fix head underflow on XDP head-grow
CVE-2026-72209 9.8 CRITICAL ntfs: validate attribute values on lookup
CVE-2026-72211 9.8 CRITICAL ntfs: grow index root value before reparent header update
CVE-2026-72210 9.8 CRITICAL ntfs: fix off-by-one in mapping pairs decoding bounds checks

Showing top 20 of 845 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

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