{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-68377","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","state":"PUBLISHED","assignerShortName":"Linux","dateReserved":"2026-07-30T09:28:09.386Z","datePublished":"2026-08-10T12:03:55.643Z","dateUpdated":"2026-08-19T16:34:38.220Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-08-19T16:34:38.220Z"},"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: act_tunnel_key: Defer dst_release to RCU callback\n\nFix a race-condition use-after-free in tunnel_key_release_params().\n\nThe function releases the metadata_dst of the old params synchronously\nvia dst_release() while deferring the params struct free with\nkfree_rcu(). A concurrent tunnel_key_act() reader on the datapath may\nstill hold the old params pointer (under rcu_read_lock_bh) and proceed\nto call dst_clone(&params->tcft_enc_metadata->dst) after the writer's\ndst_release has already pushed the dst's rcuref to RCUREF_DEAD.\n\nzdi-disclosures@trendmicro.com produced a poc which i (and Victor) verified\nthat KASAN reports:\n\n==================================================================\nBUG: KASAN: slab-use-after-free in instrument_atomic_read_write include/linux/instrumented.h:112\nBUG: KASAN: slab-use-after-free in atomic_sub_return_release include/linux/atomic/atomic-instrumented.h:326\nBUG: KASAN: slab-use-after-free in __rcuref_put include/linux/rcuref.h:109\nBUG: KASAN: slab-use-after-free in rcuref_put include/linux/rcuref.h:173\nBUG: KASAN: slab-use-after-free in dst_release+0x5b/0x370 net/core/dst.c:168\nWrite of size 4 at addr ffff88806158de40 by task poc/9388\n\nCPU: 0 UID: 0 PID: 9388 Comm: poc Tainted: G        W           7.1.0-rc7 #7 PREEMPT(lazy)\nTainted: [W]=WARN\nHardware 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\nCall Trace:\n <TASK>\n __dump_stack lib/dump_stack.c:94\n dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120\n print_address_description mm/kasan/report.c:378\n print_report+0x139/0x4ad mm/kasan/report.c:482\n kasan_report+0xe4/0x1d0 mm/kasan/report.c:595\n check_region_inline mm/kasan/generic.c:186\n kasan_check_range+0x125/0x200 mm/kasan/generic.c:200\n instrument_atomic_read_write include/linux/instrumented.h:112\n atomic_sub_return_release include/linux/atomic/atomic-instrumented.h:326\n __rcuref_put include/linux/rcuref.h:109\n rcuref_put include/linux/rcuref.h:173\n dst_release+0x5b/0x370 net/core/dst.c:168\n refdst_drop include/net/dst.h:272\n skb_dst_drop include/net/dst.h:284\n skb_release_head_state+0x293/0x400 net/core/skbuff.c:1163\n skb_release_all net/core/skbuff.c:1187\n[..]\nAllocated by task 9391:\n kasan_save_stack+0x30/0x50 mm/kasan/common.c:57\n kasan_save_track+0x14/0x30 mm/kasan/common.c:78\n poison_kmalloc_redzone mm/kasan/common.c:398\n __kasan_kmalloc+0x9a/0xb0 mm/kasan/common.c:415\n kasan_kmalloc include/linux/kasan.h:263\n __do_kmalloc_node mm/slub.c:5296\n __kmalloc_noprof+0x2f1/0x830 mm/slub.c:5308\n kmalloc_noprof include/linux/slab.h:954\n kzalloc_noprof include/linux/slab.h:1188\n offload_action_alloc+0x2f/0x130 net/core/flow_offload.c:35\n tcf_action_offload_add_ex+0x1ba/0x880 net/sched/act_api.c:258\n tcf_action_offload_add net/sched/act_api.c:293\n tcf_action_init+0x66e/0xa20 net/sched/act_api.c:1547\n tcf_action_add+0xf6/0x5d0 net/sched/act_api.c:2101\n[..]\nFreed by task 9391:\n kasan_save_stack+0x30/0x50 mm/kasan/common.c:57\n kasan_save_track+0x14/0x30 mm/kasan/common.c:78\n kasan_save_free_info+0x3b/0x70 mm/kasan/generic.c:584\n poison_slab_object mm/kasan/common.c:253\n __kasan_slab_free+0x6b/0x90 mm/kasan/common.c:285\n kasan_slab_free include/linux/kasan.h:235\n slab_free_hook mm/slub.c:2689\n slab_free mm/slub.c:6251\n kfree+0x21f/0x6b0 mm/slub.c:6566\n tcf_action_offload_add_ex+0x4ad/0x880 net/sched/act_api.c:284\n tcf_action_offload_add net/sched/act_api.c:293\n tcf_action_init+0x66e/0xa20 net/sched/act_api.c:1547\n tcf_action_add+0xf6/0x5d0 net/sched/act_api.c:2101\n\nThe buggy address belongs to the object at ffff88806158de00\n which belongs to the cache kmalloc-256 of size 256\nThe buggy address is located 64 bytes inside of\n freed 256-byte region [ffff88806158de00, ffff88806158df00)\n\nThe buggy address belongs to the physical page:\npage: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff88806158d600 pfn:0x6158c\nhead: order:1 mapcount:0 entire_map\n---truncated---"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7.8,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:L - The vulnerable window is opened via the tc/rtnetlink RTM_NEWACTION path (`tc action replace ... tunnel_key set`) and closed by locally generated traffic through a clsact/ingress filter, both requiring local system access rather than remote packets.\nAC:L - The attacker controls both sides of the race — one thread repeatedly replaces the tunnel_key action while another pumps packets through the filter — and can widen the window with qdisc backlog, so the UAF is reliably reproducible (a ZDI PoC reproduced it under KASAN).\nPR:L - The action-add path is gated only by netlink_capable(skb, CAP_NET_ADMIN), which is namespace-relative and obtainable by any unprivileged user via `unshare -Urn`; the packet side runs in the attacker's own netns.\nUI:N - Both the netlink action replace and the packet transmission that dereferences the stale params are performed entirely by the attacker's own processes; no victim action is involved.\nS:U - The corruption is confined to kernel heap memory within the same security authority; there is no VM, IOMMU, or sandbox boundary crossed.\nC:H - The freed metadata_dst sits in the general-purpose kmalloc-256 cache and remains attached to an skb, so tx paths read tunnel metadata out of reclaimed memory, giving an attacker who sprays the slab a route to disclose kernel data and defeat KASLR.\nI:H - The stale dst_clone/skb_dst_drop pair performs atomic 4-byte read-modify-write operations on a freed, attacker-reclaimable slab object, yielding a refcount-corruption primitive that is a well-established stepping stone to arbitrary write and privilege escalation.\nA:H - The use-after-free reliably corrupts slab memory and triggers KASAN-reported faults; unmitigated it causes kernel oops or panic, and the race can be repeated at will by an unprivileged user."}]}],"affected":[{"product":"Linux","vendor":"Linux","defaultStatus":"unaffected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/sched/act_tunnel_key.c"],"versions":[{"version":"9174c3df1cd181c14913138d50ccbe539bb08335","lessThan":"b5931f020b681fdcb9378262d89b61cb3c7ebbf8","status":"affected","versionType":"git"},{"version":"9174c3df1cd181c14913138d50ccbe539bb08335","lessThan":"389d03992dabb80488228e8119b9dd6d0f58e1a6","status":"affected","versionType":"git"},{"version":"9174c3df1cd181c14913138d50ccbe539bb08335","lessThan":"676ad6aa7cec89a08d2a5ce3cd5959e313f29733","status":"affected","versionType":"git"},{"version":"9174c3df1cd181c14913138d50ccbe539bb08335","lessThan":"531dbb5bb98e52ad26be7e90f9f8bec707c5bd0e","status":"affected","versionType":"git"},{"version":"9174c3df1cd181c14913138d50ccbe539bb08335","lessThan":"2200a00ff247f70f5dcdb4e6f14b0d48ddac5467","status":"affected","versionType":"git"},{"version":"9174c3df1cd181c14913138d50ccbe539bb08335","lessThan":"fed1b1ddab41a0e7a462ac690a0c8af6ff793624","status":"affected","versionType":"git"},{"version":"9174c3df1cd181c14913138d50ccbe539bb08335","lessThan":"2791a501da508b704a617b4dba29db54a65bc9f7","status":"affected","versionType":"git"},{"version":"9174c3df1cd181c14913138d50ccbe539bb08335","lessThan":"f1f5c8a3955f8fda3f84ed883ac8daa1847e724c","status":"affected","versionType":"git"},{"version":"02239e797ac75f89a05622a27d04695f08c1ca89","status":"affected","versionType":"git"},{"version":"ca9b7a65a2c97579fcdd509d454d48e3a5c49af8","status":"affected","versionType":"git"},{"version":"4.19.19","lessThan":"4.20","status":"affected","versionType":"semver"},{"version":"4.20.6","lessThan":"4.21","status":"affected","versionType":"semver"}]},{"product":"Linux","vendor":"Linux","defaultStatus":"affected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/sched/act_tunnel_key.c"],"versions":[{"version":"5.0","status":"affected"},{"version":"0","lessThan":"5.0","status":"unaffected","versionType":"semver"},{"version":"5.10.265","lessThanOrEqual":"5.10.*","status":"unaffected","versionType":"semver"},{"version":"5.15.216","lessThanOrEqual":"5.15.*","status":"unaffected","versionType":"semver"},{"version":"6.1.183","lessThanOrEqual":"6.1.*","status":"unaffected","versionType":"semver"},{"version":"6.6.148","lessThanOrEqual":"6.6.*","status":"unaffected","versionType":"semver"},{"version":"6.12.101","lessThanOrEqual":"6.12.*","status":"unaffected","versionType":"semver"},{"version":"6.18.42","lessThanOrEqual":"6.18.*","status":"unaffected","versionType":"semver"},{"version":"7.1.6","lessThanOrEqual":"7.1.*","status":"unaffected","versionType":"semver"},{"version":"7.2","lessThanOrEqual":"*","status":"unaffected","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.0","versionEndExcluding":"5.10.265"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.0","versionEndExcluding":"5.15.216"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.0","versionEndExcluding":"6.1.183"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.0","versionEndExcluding":"6.6.148"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.0","versionEndExcluding":"6.12.101"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.0","versionEndExcluding":"6.18.42"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.0","versionEndExcluding":"7.1.6"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.0","versionEndExcluding":"7.2"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.19.19"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.20.6"}]}]}],"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"}],"title":"net/sched: act_tunnel_key: Defer dst_release to RCU callback","x_generator":{"engine":"bippy-1.2.0"}}}}