--- id: CVE-2026-68377 title: 'net/sched: act_tunnel_key: Defer dst_release to RCU callback' summary: |- 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_ds… severity: high cvss: 7.8 cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H' cvssSource: cna vendor: Linux product: Linux affected: - >- Linux >= 9174c3df1cd181c14913138d50ccbe539bb08335 < b5931f020b681fdcb9378262d89b61cb3c7ebbf8 - >- Linux >= 9174c3df1cd181c14913138d50ccbe539bb08335 < 389d03992dabb80488228e8119b9dd6d0f58e1a6 - >- Linux >= 9174c3df1cd181c14913138d50ccbe539bb08335 < 676ad6aa7cec89a08d2a5ce3cd5959e313f29733 - >- Linux >= 9174c3df1cd181c14913138d50ccbe539bb08335 < 531dbb5bb98e52ad26be7e90f9f8bec707c5bd0e - >- Linux >= 9174c3df1cd181c14913138d50ccbe539bb08335 < 2200a00ff247f70f5dcdb4e6f14b0d48ddac5467 - >- Linux >= 9174c3df1cd181c14913138d50ccbe539bb08335 < fed1b1ddab41a0e7a462ac690a0c8af6ff793624 - >- Linux >= 9174c3df1cd181c14913138d50ccbe539bb08335 < 2791a501da508b704a617b4dba29db54a65bc9f7 - >- Linux >= 9174c3df1cd181c14913138d50ccbe539bb08335 < f1f5c8a3955f8fda3f84ed883ac8daa1847e724c - Linux 02239e797ac75f89a05622a27d04695f08c1ca89 - Linux ca9b7a65a2c97579fcdd509d454d48e3a5c49af8 - Linux >= 4.19.19 < 4.20 - Linux >= 4.20.6 < 4.21 - Linux 5.0 ssvc: exploitation: none automatable: 'no' technicalImpact: total timestamp: '2026-10-16T15:47:38.441696Z' published: '2026-08-10' updated: '2026-10-16' sourceUpdated: '2026-10-16T15:53:10.105Z' source: CVEORG sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-68377' references: - url: 'https://git.kernel.org/stable/c/b5931f020b681fdcb9378262d89b61cb3c7ebbf8' - url: 'https://git.kernel.org/stable/c/389d03992dabb80488228e8119b9dd6d0f58e1a6' - url: 'https://git.kernel.org/stable/c/676ad6aa7cec89a08d2a5ce3cd5959e313f29733' - url: 'https://git.kernel.org/stable/c/531dbb5bb98e52ad26be7e90f9f8bec707c5bd0e' - url: 'https://git.kernel.org/stable/c/2200a00ff247f70f5dcdb4e6f14b0d48ddac5467' - url: 'https://git.kernel.org/stable/c/fed1b1ddab41a0e7a462ac690a0c8af6ff793624' - url: 'https://git.kernel.org/stable/c/2791a501da508b704a617b4dba29db54a65bc9f7' - url: 'https://git.kernel.org/stable/c/f1f5c8a3955f8fda3f84ed883ac8daa1847e724c' tags: - cve.org epss: 0.00128 epssPercentile: 0.02155 ingestedAt: '2026-10-16T17:24:46.864Z' --- ## Overview 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(¶ms->tcft_enc_metadata->dst) after the writer's dst_release has already pushed the dst's rcuref to RCUREF_DEAD. zdi-disclosures@trendmicro.com 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: __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--- ## Affected - `Linux >= 9174c3df1cd181c14913138d50ccbe539bb08335 < b5931f020b681fdcb9378262d89b61cb3c7ebbf8` - `Linux >= 9174c3df1cd181c14913138d50ccbe539bb08335 < 389d03992dabb80488228e8119b9dd6d0f58e1a6` - `Linux >= 9174c3df1cd181c14913138d50ccbe539bb08335 < 676ad6aa7cec89a08d2a5ce3cd5959e313f29733` - `Linux >= 9174c3df1cd181c14913138d50ccbe539bb08335 < 531dbb5bb98e52ad26be7e90f9f8bec707c5bd0e` - `Linux >= 9174c3df1cd181c14913138d50ccbe539bb08335 < 2200a00ff247f70f5dcdb4e6f14b0d48ddac5467` - `Linux >= 9174c3df1cd181c14913138d50ccbe539bb08335 < fed1b1ddab41a0e7a462ac690a0c8af6ff793624` - `Linux >= 9174c3df1cd181c14913138d50ccbe539bb08335 < 2791a501da508b704a617b4dba29db54a65bc9f7` - `Linux >= 9174c3df1cd181c14913138d50ccbe539bb08335 < f1f5c8a3955f8fda3f84ed883ac8daa1847e724c` - `Linux 02239e797ac75f89a05622a27d04695f08c1ca89` - `Linux ca9b7a65a2c97579fcdd509d454d48e3a5c49af8` - `Linux >= 4.19.19 < 4.20` - `Linux >= 4.20.6 < 4.21` - `Linux 5.0` ## Remediation Refer to the linked advisories for vendor-supplied fixes and affected version ranges.