CVE-2025-21707
CriticalCVSS 9.8Exploitation Probability (EPSS)
Low risk38th percentile - higher than 38% of all known CVEs
Summary
In the Linux kernel's MPTCP implementation, a vulnerability was found due to improper management of suboption status. Zeroing the bitmask before parsing is insufficient to ensure state consistency, leading to uninitialized bitfields and a KMSAN bug.
Risk Assessment
The vulnerability may cause unpredictable system behavior, including kernel panics or potential data integrity issues in MPTCP connections.
Recommendation
Immediately update the Linux kernel to a version containing the fix that consolidates MPTCP suboption status.
Other vulnerabilities in Linux kernel
See all- CVE-2026-80886Unknown
In the Linux kernel, a vulnerability in the msm serial driver was fixed by disabling DMA for the console UART. Concurrent writes from userspace and the kernel can trigger a race condition resulting in an infinite loop of the same messages. The fix disables DMA for the console UART to ensure a reliable output path.
- CVE-2026-80885Unknown
In the Linux kernel, a fix was made for an uncancelled rxrpc OOB message handler in AFS. The fix cancels OOB message processing (typically to respond to security challenges) and moves it to afs_wq so it is also waited for. The OOB handler now returns if the net namespace is no longer live.
- CVE-2026-80884Unknown
In the Linux kernel, a fix was made in the NTB driver to store the original DMA address for future release. The DMA API requires that dma_free_attrs receive the exact dma_handle originally returned by the allocation function. The fix prevents modifying it.
- CVE-2026-80883Unknown
In the Linux kernel, a fix was made in the Tegra graphics drivers (gr2d/gr3d) to initialize the address register map before the HOST1X client is registered. Previously, client registration occurred before initialization, potentially allowing userspace to submit jobs before initialization. The fix moves register initialization before client registration.
- CVE-2026-80882Unknown
In the Linux kernel, a fix was made in the Tegra crypto driver to return ENOMEM when input buffer allocation fails for ccm. The fix ensures the ENOMEM error value is set when the allocation fails in tegra_ccm_do_one_req.
- CVE-2026-80881Unknown
In the Linux kernel, a fix was made in the OCFS2 filesystem regarding buffer head management in ocfs2_read_blocks(). The fix clarifies that the caller should not assume that the buffer head returned by sb_getblk() is exclusively owned and that put_bh() always drops b_count from 1 to 0. To avoid a scenario where a buffer head remains on hold and may be returned with BH_Uptodate set despite previous validation failure, BH_Uptodate is now cleared immediately after the validate() callback detects data inconsistency.
- CVE-2026-80880Unknown
In the Linux kernel, the IB/mlx5 driver has a vulnerability related to implicit ODP and rereg_mr operation. Due to child mkeys in the implicit ODP configuration, nothing can be changed in place for the parent mkey, so the whole structure must be rebuilt. Additionally, a race condition involving access to mr->pd by child keys was removed.
- CVE-2026-80879Unknown
A circular locking dependency was found in the Linux kernel's OCFS2 filesystem during direct I/O write completion. The ocfs2_dio_end_io_write function could deadlock due to improper lock ordering involving system inodes (INODE_ALLOC, EXTENT_ALLOC, ORPHAN_DIR). The fix releases allocation contexts before acquiring the ORPHAN_DIR lock.
- CVE-2026-80878Unknown
In the Linux kernel, the AFS filesystem has a memory leak related to an ungot volume. The afs_lookup_volume_rcu() function does not release a dying volume when afs_try_get_volume() fails.
- CVE-2026-80877Unknown
In the Linux kernel, the AFS filesystem has a memory leak related to the vllist in afs_update_cell(). When the new list is empty (nr_servers == 0), the old list is not replaced, leading to a leak of the new list.
Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: mptcp: consolidate suboption status MPTCP maintains the received sub-options status is the bitmask carrying the received suboptions and in several bitfields carrying per suboption additional info. Zeroing the bitmask before parsing is not enough to ensure a consistent status, and the MPTCP code has to additionally clear some bitfiled depending on the actually parsed suboption. The above schema is fragile, and syzbot managed to trigger a path where a relevant bitfield is not cleared/initialized: BUG: KMSAN: uninit-value in __mptcp_expand_seq net/mptcp/options.c:1030 [inline] BUG: KMSAN: uninit-value in mptcp_expand_seq net/mptcp/protocol.h:864 [inline] BUG: KMSAN: uninit-value in ack_update_msk net/mptcp/options.c:1060 [inline] BUG: KMSAN: uninit-value in mptcp_incoming_options+0x2036/0x3d30 net/mptcp/options.c:1209 __mptcp_expand_seq net/mptcp/options.c:1030 [inline] mptcp_expand_seq net/mptcp/protocol.h:864 [inline] ack_update_msk net/mptcp/options.c:1060 [inline] mptcp_incoming_options+0x2036/0x3d30 net/mptcp/options.c:1209 tcp_data_queue+0xb4/0x7be0 net/ipv4/tcp_input.c:5233 tcp_rcv_established+0x1061/0x2510 net/ipv4/tcp_input.c:6264 tcp_v4_do_rcv+0x7f3/0x11a0 net/ipv4/tcp_ipv4.c:1916 tcp_v4_rcv+0x51df/0x5750 net/ipv4/tcp_ipv4.c:2351 ip_protocol_deliver_rcu+0x2a3/0x13d0 net/ipv4/ip_input.c:205 ip_local_deliver_finish+0x336/0x500 net/ipv4/ip_input.c:233 NF_HOOK include/linux/netfilter.h:314 [inline] ip_local_deliver+0x21f/0x490 net/ipv4/ip_input.c:254 dst_input include/net/dst.h:460 [inline] ip_rcv_finish+0x4a2/0x520 net/ipv4/ip_input.c:447 NF_HOOK include/linux/netfilter.h:314 [inline] ip_rcv+0xcd/0x380 net/ipv4/ip_input.c:567 __netif_receive_skb_one_core net/core/dev.c:5704 [inline] __netif_receive_skb+0x319/0xa00 net/core/dev.c:5817 process_backlog+0x4ad/0xa50 net/core/dev.c:6149 __napi_poll+0xe7/0x980 net/core/dev.c:6902 napi_poll net/core/dev.c:6971 [inline] net_rx_action+0xa5a/0x19b0 net/core/dev.c:7093 handle_softirqs+0x1a0/0x7c0 kernel/softirq.c:561 __do_softirq+0x14/0x1a kernel/softirq.c:595 do_softirq+0x9a/0x100 kernel/softirq.c:462 __local_bh_enable_ip+0x9f/0xb0 kernel/softirq.c:389 local_bh_enable include/linux/bottom_half.h:33 [inline] rcu_read_unlock_bh include/linux/rcupdate.h:919 [inline] __dev_queue_xmit+0x2758/0x57d0 net/core/dev.c:4493 dev_queue_xmit include/linux/netdevice.h:3168 [inline] neigh_hh_output include/net/neighbour.h:523 [inline] neigh_output include/net/neighbour.h:537 [inline] ip_finish_output2+0x187c/0x1b70 net/ipv4/ip_output.c:236 __ip_finish_output+0x287/0x810 ip_finish_output+0x4b/0x600 net/ipv4/ip_output.c:324 NF_HOOK_COND include/linux/netfilter.h:303 [inline] ip_output+0x15f/0x3f0 net/ipv4/ip_output.c:434 dst_output include/net/dst.h:450 [inline] ip_local_out net/ipv4/ip_output.c:130 [inline] __ip_queue_xmit+0x1f2a/0x20d0 net/ipv4/ip_output.c:536 ip_queue_xmit+0x60/0x80 net/ipv4/ip_output.c:550 __tcp_transmit_skb+0x3cea/0x4900 net/ipv4/tcp_output.c:1468 tcp_transmit_skb net/ipv4/tcp_output.c:1486 [inline] tcp_write_xmit+0x3b90/0x9070 net/ipv4/tcp_output.c:2829 __tcp_push_pending_frames+0xc4/0x380 net/ipv4/tcp_output.c:3012 tcp_send_fin+0x9f6/0xf50 net/ipv4/tcp_output.c:3618 __tcp_close+0x140c/0x1550 net/ipv4/tcp.c:3130 __mptcp_close_ssk+0x74e/0x16f0 net/mptcp/protocol.c:2496 mptcp_close_ssk+0x26b/0x2c0 net/mptcp/protocol.c:2550 mptcp_pm_nl_rm_addr_or_subflow+0x635/0xd10 net/mptcp/pm_netlink.c:889 mptcp_pm_nl_rm_subflow_received net/mptcp/pm_netlink.c:924 [inline] mptcp_pm_flush_addrs_and_subflows net/mptcp/pm_netlink.c:1688 [inline] mptcp_nl_flush_addrs_list net/mptcp/pm_netlink.c:1709 [inline] mptcp_pm_nl_flush_addrs_doit+0xe10/0x1630 net/mptcp/pm_netlink.c:1750 genl_family_rcv_msg_doit net/netlink/genetlink.c:1115 [inline] ---truncated---