CVE-2025-38590 in Linux
Summary
by MITRE • 08/19/2025
In the Linux kernel, the following vulnerability has been resolved:
net/mlx5e: Remove skb secpath if xfrm state is not found
Hardware returns a unique identifier for a decrypted packet's xfrm state, this state is looked up in an xarray. However, the state might have been freed by the time of this lookup.
Currently, if the state is not found, only a counter is incremented. The secpath (sp) extension on the skb is not removed, resulting in sp->len becoming 0.
Subsequently, functions like __xfrm_policy_check() attempt to access fields such as xfrm_input_state(skb)->xso.type (which dereferences sp->xvec[sp->len - 1]) without first validating sp->len. This leads to
a crash when dereferencing an invalid state pointer.
This patch prevents the crash by explicitly removing the secpath extension from the skb if the xfrm state is not found after hardware decryption. This ensures downstream functions do not operate on a zero-length secpath.
BUG: unable to handle page fault for address: ffffffff000002c8 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 282e067 P4D 282e067 PUD 0 Oops: Oops: 0000 [#1] SMP
CPU: 12 UID: 0 PID: 0 Comm: swapper/12 Not tainted 6.15.0-rc7_for_upstream_min_debug_2025_05_27_22_44 #1 NONE Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014 RIP: 0010:__xfrm_policy_check+0x61a/0xa30 Code: b6 77 7f 83 e6 02 74 14 4d 8b af d8 00 00 00 41 0f b6 45 05 c1 e0 03 48 98 49 01 c5 41 8b 45 00 83 e8 01 48 98 49 8b 44 c5 10 <0f> b6 80 c8 02 00 00 83 e0 0c 3c 04 0f 84 0c 02 00 00 31 ff 80 fa RSP: 0018:ffff88885fb04918 EFLAGS: 00010297 RAX: ffffffff00000000 RBX: 0000000000000002 RCX: 0000000000000000 RDX: 0000000000000002 RSI: 0000000000000002 RDI: 0000000000000000 RBP: ffffffff8311af80 R08: 0000000000000020 R09: 00000000c2eda353 R10: ffff88812be2bbc8 R11: 000000001faab533 R12: ffff88885fb049c8 R13: ffff88812be2bbc8 R14: 0000000000000000 R15: ffff88811896ae00 FS: 0000000000000000(0000) GS:ffff8888dca82000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: ffffffff000002c8 CR3: 0000000243050002 CR4: 0000000000372eb0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: <IRQ> ? try_to_wake_up+0x108/0x4c0 ? udp4_lib_lookup2+0xbe/0x150 ? udp_lib_lport_inuse+0x100/0x100 ? __udp4_lib_lookup+0x2b0/0x410 __xfrm_policy_check2.constprop.0+0x11e/0x130 udp_queue_rcv_one_skb+0x1d/0x530 udp_unicast_rcv_skb+0x76/0x90 __udp4_lib_rcv+0xa64/0xe90 ip_protocol_deliver_rcu+0x20/0x130 ip_local_deliver_finish+0x75/0xa0 ip_local_deliver+0xc1/0xd0 ? ip_protocol_deliver_rcu+0x130/0x130 ip_sublist_rcv+0x1f9/0x240 ? ip_rcv_finish_core+0x430/0x430 ip_list_rcv+0xfc/0x130 __netif_receive_skb_list_core+0x181/0x1e0 netif_receive_skb_list_internal+0x200/0x360 ? mlx5e_build_rx_skb+0x1bc/0xda0 [mlx5_core]
gro_receive_skb+0xfd/0x210 mlx5e_handle_rx_cqe_mpwrq+0x141/0x280 [mlx5_core]
mlx5e_poll_rx_cq+0xcc/0x8e0 [mlx5_core]
? mlx5e_handle_rx_dim+0x91/0xd0 [mlx5_core]
mlx5e_napi_poll+0x114/0xab0 [mlx5_core]
__napi_poll+0x25/0x170 net_rx_action+0x32d/0x3a0 ? mlx5_eq_comp_int+0x8d/0x280 [mlx5_core]
? notifier_call_chain+0x33/0xa0 handle_softirqs+0xda/0x250 irq_exit_rcu+0x6d/0xc0 common_interrupt+0x81/0xa0 </IRQ>
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Analysis
by VulDB Data Team • 12/15/2025
The vulnerability described in CVE-2025-38590 resides within the Linux kernel's networking subsystem, specifically affecting the mlx5e driver responsible for Mellanox ConnectX network adapters. The issue manifests during hardware-assisted decryption of packets, where the kernel attempts to locate the corresponding xfrm state using a unique identifier returned by the hardware. This identifier is used to perform a lookup in an xarray data structure that stores xfrm states. However, race conditions or memory management events may cause the xfrm state to be freed before the lookup completes, leading to a scenario where the state is not found during the lookup process.
When the xfrm state cannot be located, the current implementation only increments a counter without properly handling the associated security path (secpath) extension on the socket buffer (skb). This results in the secpath length (sp->len) remaining non-zero despite the underlying state being invalid. Subsequently, functions such as __xfrm_policy_check attempt to access fields within the xfrm state without validating that the secpath contains valid data. Specifically, the function dereferences sp->xvec[sp->len - 1] which points to an invalid memory location when sp->len is zero, causing a kernel page fault and resulting in a system crash. This vulnerability directly maps to CWE-125: Uninitialized Memory Read, as it involves accessing memory that has been freed or not properly initialized.
The crash occurs in the kernel's networking stack when processing decrypted packets received through the mlx5e driver. The stack trace reveals that the failure originates in __xfrm_policy_check where it attempts to access xfrm_input_state(skb)->xso.type, which requires valid entries in the secpath vector. The fault address ff9ffffff000002c8 indicates a memory access to an invalid pointer, likely due to the zero-length secpath structure. This issue is particularly critical for systems using hardware offloading for IPsec encryption, as it can cause complete system hangs or crashes when processing certain decrypted packets, especially in high-throughput environments where such race conditions are more likely to occur.
The fix implemented in this patch addresses the root cause by explicitly removing the secpath extension from the skb when the xfrm state is not found after hardware decryption. This ensures that downstream functions do not attempt to operate on a zero-length secpath structure, thereby preventing the invalid memory access. The mitigation aligns with ATT&CK technique T1059.006 for kernel-level code execution and addresses the broader category of kernel memory corruption vulnerabilities. Organizations using Mellanox network adapters with hardware offloading for IPsec should apply this patch immediately, as the vulnerability can be exploited to cause denial of service or potentially escalate privileges depending on the specific system configuration. The fix demonstrates proper defensive programming practices by ensuring resource cleanup and validation before memory access operations, which is essential for maintaining kernel stability in high-performance networking environments.