CVE-2025-38491
Linux Kernel 5.10.228 – 5.11
Raw vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:HSummary
CVE-2025-38491 is a medium-severity Improper Locking (CWE-667) vulnerability in Linux Linux Kernel. Its CVSS base score is 5.5 (Medium).
Operationally, ranked at the 1th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified map to SI-2 (Flaw Remediation) and CM-7 (Least Functionality) — see the control section below for these in your framework.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2025-22872
Vulnerability Data
In the Linux kernel, the following vulnerability has been resolved: mptcp: make fallback action and fallback decision atomic Syzkaller reported the following splat: WARNING: CPU: 1 PID: 7704 at net/mptcp/protocol.h:1223 __mptcp_do_fallback net/mptcp/protocol.h:1223 [inline] WARNING: CPU: 1 PID: 7704 at net/mptcp/protocol.h:1223…
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mptcp_do_fallback net/mptcp/protocol.h:1244 [inline] WARNING: CPU: 1 PID: 7704 at net/mptcp/protocol.h:1223 check_fully_established net/mptcp/options.c:982 [inline] WARNING: CPU: 1 PID: 7704 at net/mptcp/protocol.h:1223 mptcp_incoming_options+0x21a8/0x2510 net/mptcp/options.c:1153 Modules linked in: CPU: 1 UID: 0 PID: 7704 Comm: syz.3.1419 Not tainted 6.16.0-rc3-gbd5ce2324dba #20 PREEMPT(voluntary) Hardware name: QEMU Ubuntu 24.04 PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 RIP: 0010:__mptcp_do_fallback net/mptcp/protocol.h:1223 [inline] RIP: 0010:mptcp_do_fallback net/mptcp/protocol.h:1244 [inline] RIP: 0010:check_fully_established net/mptcp/options.c:982 [inline] RIP: 0010:mptcp_incoming_options+0x21a8/0x2510 net/mptcp/options.c:1153 Code: 24 18 e8 bb 2a 00 fd e9 1b df ff ff e8 b1 21 0f 00 e8 ec 5f c4 fc 44 0f b7 ac 24 b0 00 00 00 e9 54 f1 ff ff e8 d9 5f c4 fc 90 <0f> 0b 90 e9 b8 f4 ff ff e8 8b 2a 00 fd e9 8d e6 ff ff e8 81 2a 00 RSP: 0018:ffff8880a3f08448 EFLAGS: 00010246 RAX: 0000000000000000 RBX: ffff8880180a8000 RCX: ffffffff84afcf45 RDX: ffff888090223700 RSI: ffffffff84afdaa7 RDI: 0000000000000001 RBP: ffff888017955780 R08: 0000000000000001 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 R13: ffff8880180a8910 R14: ffff8880a3e9d058 R15: 0000000000000000 FS: 00005555791b8500(0000) GS:ffff88811c495000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000000110c2800b7 CR3: 0000000058e44000 CR4: 0000000000350ef0 Call Trace: <IRQ> tcp_reset+0x26f/0x2b0 net/ipv4/tcp_input.c:4432 tcp_validate_incoming+0x1057/0x1b60 net/ipv4/tcp_input.c:5975 tcp_rcv_established+0x5b5/0x21f0 net/ipv4/tcp_input.c:6166 tcp_v4_do_rcv+0x5dc/0xa70 net/ipv4/tcp_ipv4.c:1925 tcp_v4_rcv+0x3473/0x44a0 net/ipv4/tcp_ipv4.c:2363 ip_protocol_deliver_rcu+0xba/0x480 net/ipv4/ip_input.c:205 ip_local_deliver_finish+0x2f1/0x500 net/ipv4/ip_input.c:233 NF_HOOK include/linux/netfilter.h:317 [inline] NF_HOOK include/linux/netfilter.h:311 [inline] ip_local_deliver+0x1be/0x560 net/ipv4/ip_input.c:254 dst_input include/net/dst.h:469 [inline] ip_rcv_finish net/ipv4/ip_input.c:447 [inline] NF_HOOK include/linux/netfilter.h:317 [inline] NF_HOOK include/linux/netfilter.h:311 [inline] ip_rcv+0x514/0x810 net/ipv4/ip_input.c:567 __netif_receive_skb_one_core+0x197/0x1e0 net/core/dev.c:5975 __netif_receive_skb+0x1f/0x120 net/core/dev.c:6088 process_backlog+0x301/0x1360 net/core/dev.c:6440 __napi_poll.constprop.0+0xba/0x550 net/core/dev.c:7453 napi_poll net/core/dev.c:7517 [inline] net_rx_action+0xb44/0x1010 net/core/dev.c:7644 handle_softirqs+0x1d0/0x770 kernel/softirq.c:579 do_softirq+0x3f/0x90 kernel/softirq.c:480 </IRQ> <TASK> __local_bh_enable_ip+0xed/0x110 kernel/softirq.c:407 local_bh_enable include/linux/bottom_half.h:33 [inline] inet_csk_listen_stop+0x2c5/0x1070 net/ipv4/inet_connection_sock.c:1524 mptcp_check_listen_stop.part.0+0x1cc/0x220 net/mptcp/protocol.c:2985 mptcp_check_listen_stop net/mptcp/mib.h:118 [inline] __mptcp_close+0x9b9/0xbd0 net/mptcp/protocol.c:3000 mptcp_close+0x2f/0x140 net/mptcp/protocol.c:3066 inet_release+0xed/0x200 net/ipv4/af_inet.c:435 inet6_release+0x4f/0x70 net/ipv6/af_inet6.c:487 __sock_release+0xb3/0x270 net/socket.c:649 sock_close+0x1c/0x30 net/socket.c:1439 __fput+0x402/0xb70 fs/file_table.c:465 task_work_run+0x150/0x240 kernel/task_work.c:227 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline] exit_to_user_mode_loop+0xd4 ---truncated---
- CWE(s)
Related Threats
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
Mitigating Controls (NIST 800-53 r5) AI
Directly addresses the root cause by requiring application of the kernel patch that makes MPTCP fallback action and decision atomic.
Disabling MPTCP (or restricting its use to only required configurations) removes the vulnerable code path entirely.
Kernel log monitoring and anomaly detection can identify the exact WARNING splat in mptcp_incoming_options when the race occurs.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Secure SDLC practices directly include code reviews, static analysis, and concurrency standards that prevent improper locking.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Security testing can detect race conditions and locking errors before release.
Secure development lifecycle includes concurrency and locking requirements that reduce improper locking defects.
Application security requirements can mandate proper lock acquisition/release patterns.
Secure architecture principles address thread-safety and resource synchronization.
Secure coding standards directly prohibit missing or incorrect lock usage.
Change management may catch locking issues introduced by modifications but does not prevent the weakness itself.