CVE-2026-68377

Status: UPDATED  |  Advisory ID: CVE-2026-68377

Key Details

Affected Products, Subsystems & Sectors

What to Know

In the Linux kernel, the following vulnerability has been resolved:

net/sched: act_tunnel_key: Defer dst_release to RCU callback

Fix a race-condition use-after-free in tunnel_key_release_params().

The function releases the metadata_dst of the old params synchronously

via dst_release() while deferring the params struct free with

kfree_rcu(). A concurrent tunnel_key_act() reader on the datapath may

still hold the old params pointer (under rcu_read_lock_bh) and proceed

to call dst_clone(&params->tcft_enc_metadata->dst) after the writer's

dst_release has already pushed the dst's rcuref to RCUREF_DEAD.

[email protected] produced a poc which i (and Victor) verified

that KASAN reports:

==================================================================

BUG: KASAN: slab-use-after-free in instrument_atomic_read_write include/linux/instrumented.h:112

BUG: KASAN: slab-use-after-free in atomic_sub_return_release include/linux/atomic/atomic-instrumented.h:326

BUG: KASAN: slab-use-after-free in __rcuref_put include/linux/rcuref.h:109

BUG: KASAN: slab-use-after-free in rcuref_put include/linux/rcuref.h:173

BUG: KASAN: slab-use-after-free in dst_release+0x5b/0x370 net/core/dst.c:168

Write of size 4 at addr ffff88806158de40 by task poc/9388

CPU: 0 UID: 0 PID: 9388 Comm: poc Tainted: G W 7.1.0-rc7 #7 PREEMPT(lazy)

Tainted: [W]=WARN

Hardware name: QEMU Ubuntu 25.10 PC v2 (i440FX + PIIX, + 10.1 machine, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014

Call Trace:

<TASK>

__dump_stack lib/dump_stack.c:94

dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120

print_address_description mm/kasan/report.c:378

print_report+0x139/0x4ad mm/kasan/report.c:482

kasan_report+0xe4/0x1d0 mm/kasan/report.c:595

check_region_inline mm/kasan/generic.c:186

kasan_check_range+0x125/0x200 mm/kasan/generic.c:200

instrument_atomic_read_write include/linux/instrumented.h:112

atomic_sub_return_release include/linux/atomic/atomic-instrumented.h:326

__rcuref_put include/linux/rcuref.h:109

rcuref_put include/linux/rcuref.h:173

dst_release+0x5b/0x370 net/core/dst.c:168

refdst_drop include/net/dst.h:272

skb_dst_drop include/net/dst.h:284

skb_release_head_state+0x293/0x400 net/core/skbuff.c:1163

skb_release_all net/core/skbuff.c:1187

[..]

Allocated by task 9391:

kasan_save_stack+0x30/0x50 mm/kasan/common.c:57

kasan_save_track+0x14/0x30 mm/kasan/common.c:78

poison_kmalloc_redzone mm/kasan/common.c:398

__kasan_kmalloc+0x9a/0xb0 mm/kasan/common.c:415

kasan_kmalloc include/linux/kasan.h:263

__do_kmalloc_node mm/slub.c:5296

__kmalloc_noprof+0x2f1/0x830 mm/slub.c:5308

kmalloc_noprof include/linux/slab.h:954

kzalloc_noprof include/linux/slab.h:1188

offload_action_alloc+0x2f/0x130 net/core/flow_offload.c:35

tcf_action_offload_add_ex+0x1ba/0x880 net/sched/act_api.c:258

tcf_action_offload_add net/sched/act_api.c:293

tcf_action_init+0x66e/0xa20 net/sched/act_api.c:1547

tcf_action_add+0xf6/0x5d0 net/sched/act_api.c:2101

[..]

Freed by task 9391:

kasan_save_stack+0x30/0x50 mm/kasan/common.c:57

kasan_save_track+0x14/0x30 mm/kasan/common.c:78

kasan_save_free_info+0x3b/0x70 mm/kasan/generic.c:584

poison_slab_object mm/kasan/common.c:253

__kasan_slab_free+0x6b/0x90 mm/kasan/common.c:285

kasan_slab_free include/linux/kasan.h:235

slab_free_hook mm/slub.c:2689

slab_free mm/slub.c:6251

kfree+0x21f/0x6b0 mm/slub.c:6566

tcf_action_offload_add_ex+0x4ad/0x880 net/sched/act_api.c:284

tcf_action_offload_add net/sched/act_api.c:293

tcf_action_init+0x66e/0xa20 net/sched/act_api.c:1547

tcf_action_add+0xf6/0x5d0 net/sched/act_api.c:2101

The buggy address belongs to the object at ffff88806158de00

which belongs to the cache kmalloc-256 of size 256

The buggy address is located 64 bytes inside of

freed 256-byte region [ffff88806158de00, ffff88806158df00)

The buggy address belongs to the physical page:

page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff88806158d600 pfn:0x6158c

head: order:1 mapcount:0 entire_map

---truncated--- (NVD)

What to Do

Monitor Linux's web page for any future patch releases.

References