CVE-2025-21674: net/mlx5e: Fix inversion dependency warning while enabling IPsec tunnel
In the Linux kernel, the following vulnerability has been resolved:
net/mlx5e: Fix inversion dependency warning while enabling IPsec tunnel
Attempt to enable IPsec packet offload in tunnel mode in debug kernel
generates the following kernel panic, which is happening due to two
issues:
1. In SA add section, the should be _bh() variant when marking SA mode.
2. There is not needed flush_workqueue in SA delete routine. It is not
needed as at this stage as it is removed from SADB and the running work
will be canceled later in SA free.
=====================================================
WARNING: SOFTIRQ-safe -> SOFTIRQ-unsafe lock order detected
6.12.0+ #4 Not tainted
-----------------------------------------------------
charon/1337 [HC0[0]:SC0[4]:HE1:SE0] is trying to acquire:
ffff88810f365020 (&xa->xa_lock#24){+.+.}-{3:3}, at: mlx5e_xfrm_del_state+0xca/0x1e0 [mlx5_core]
and this task is already holding:
ffff88813e0f0d48 (&x->lock){+.-.}-{3:3}, at: xfrm_state_delete+0x16/0x30
which would create a new lock dependency:
(&x->lock){+.-.}-{3:3} -> (&xa->xa_lock#24){+.+.}-{3:3}
but this new dependency connects a SOFTIRQ-irq-safe lock:
(&x->lock){+.-.}-{3:3}
... which became SOFTIRQ-irq-safe at:
lock_acquire+0x1be/0x520
_raw_spin_lock_bh+0x34/0x40
xfrm_timer_handler+0x91/0xd70
__hrtimer_run_queues+0x1dd/0xa60
hrtimer_run_softirq+0x146/0x2e0
handle_softirqs+0x266/0x860
irq_exit_rcu+0x115/0x1a0
sysvec_apic_timer_interrupt+0x6e/0x90
asm_sysvec_apic_timer_interrupt+0x16/0x20
default_idle+0x13/0x20
default_idle_call+0x67/0xa0
do_idle+0x2da/0x320
cpu_startup_entry+0x50/0x60
start_secondary+0x213/0x2a0
common_startup_64+0x129/0x138
to a SOFTIRQ-irq-unsafe lock:
(&xa->xa_lock#24){+.+.}-{3:3}
... which became SOFTIRQ-irq-unsafe at:
...
lock_acquire+0x1be/0x520
_raw_spin_lock+0x2c/0x40
xa_set_mark+0x70/0x110
mlx5e_xfrm_add_state+0xe48/0x2290 [mlx5_core]
xfrm_dev_state_add+0x3bb/0xd70
xfrm_add_sa+0x2451/0x4a90
xfrm_user_rcv_msg+0x493/0x880
netlink_rcv_skb+0x12e/0x380
xfrm_netlink_rcv+0x6d/0x90
netlink_unicast+0x42f/0x740
netlink_sendmsg+0x745/0xbe0
__sock_sendmsg+0xc5/0x190
__sys_sendto+0x1fe/0x2c0
__x64_sys_sendto+0xdc/0x1b0
do_syscall_64+0x6d/0x140
entry_SYSCALL_64_after_hwframe+0x4b/0x53
other info that might help us debug this:
Possible interrupt unsafe locking scenario:
CPU0 CPU1
---- ----
lock(&xa->xa_lock#24);
local_irq_disable();
lock(&x->lock);
lock(&xa->xa_lock#24);
<Interrupt>
lock(&x->lock);
*** DEADLOCK ***
2 locks held by charon/1337:
#0: ffffffff87f8f858 (&net->xfrm.xfrm_cfg_mutex){+.+.}-{4:4}, at: xfrm_netlink_rcv+0x5e/0x90
#1: ffff88813e0f0d48 (&x->lock){+.-.}-{3:3}, at: xfrm_state_delete+0x16/0x30
the dependencies between SOFTIRQ-irq-safe lock and the holding lock:
-> (&x->lock){+.-.}-{3:3} ops: 29 {
HARDIRQ-ON-W at:
lock_acquire+0x1be/0x520
_raw_spin_lock_bh+0x34/0x40
xfrm_alloc_spi+0xc0/0xe60
xfrm_alloc_userspi+0x5f6/0xbc0
xfrm_user_rcv_msg+0x493/0x880
netlink_rcv_skb+0x12e/0x380
xfrm_netlink_rcv+0x6d/0x90
netlink_unicast+0x42f/0x740
netlink_sendmsg+0x745/0xbe0
__sock_sendmsg+0xc5/0x190
__sys_sendto+0x1fe/0x2c0
__x64_sys_sendto+0xdc/0x1b0
do_syscall_64+0x6d/0x140
entry_SYSCALL_64_after_hwframe+0x4b/0x53
IN-SOFTIRQ-W at:
lock_acquire+0x1be/0x520
_raw_spin_lock_bh+0x34/0x40
xfrm_timer_handler+0x91/0xd70
__hrtimer_run_queues+0x1dd/0xa60
---truncated---
Security readout for executives and security teams
Plain-English summary
CVE-2025-21674 is a Linux kernel availability bug in the mlx5e networking path when enabling IPsec packet offload in tunnel mode. On affected systems, a local privileged user can trigger a kernel panic, causing service disruption. It does not indicate data theft or integrity compromise.
Executive priority
Medium priority. Address during normal kernel patch cycles, faster for VPN, firewall, gateway, or high-availability systems that use mlx5e IPsec offload. Business risk is outage potential, not confirmed data exposure.
Technical view
The issue is a lock-ordering flaw, CWE-667, in mlx5e XFRM/IPsec offload handling. The CVE describes an incorrect non-_bh lock marking path and an unnecessary workqueue flush during SA deletion, producing a SOFTIRQ-safe to unsafe dependency and possible deadlock/panic in debug kernels.
Likely exposure
Exposure is most likely on Linux systems using the mlx5e driver with IPsec packet offload in tunnel mode. The CVE lists local, low-complexity, low-privilege access and high availability impact. Systems not using this driver path or feature appear less exposed based on the source bundle.
Exploitation context
The source bundle does not show public exploitation or KEV listing. The described trigger requires local access and IPsec/XFRM activity involving mlx5e packet offload tunnel mode. Treat this as an availability risk rather than a remote compromise based on current evidence.
Researcher notes
Evidence is limited to the CVE text and Linux stable references. The affected version data in the bundle is incomplete or normalized, so researchers should confirm exact vulnerable and fixed ranges from upstream commits or distribution advisories before declaring exposure.
Mitigation direction
Apply the relevant Linux stable kernel fixes referenced by the CVE.
Check your distribution vendor advisories for packaged kernel update availability.
Prioritize hosts using mlx5e and IPsec packet offload in tunnel mode.
If patching is delayed, review vendor guidance for feature-level workarounds.
Avoid direct wrangler or deployment assumptions; this is kernel-level remediation.
Validation and detection
Inventory Linux kernel versions against the CVE record and vendor advisories.
Identify hosts using mlx5e networking and IPsec/XFRM offload features.
Confirm whether stable commits 87c4417, 6d3d69c, or 2c368809 are included.
Review kernel logs for related lock dependency warnings or panics.
Validate updates in staging before broad production rollout.
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Potential ATT&CK relevance
Conservative CVE-to-ATT&CK context
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ATT&CK lookup starting points
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cwe · low confidence lookup
CWE-667: Exact CWE lookup
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CWE-667 · source CWE mapping
Improper Locking
Improper Locking represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.