{"api_version":"1","generated_at":"2026-10-21T11:24:10+00:00","cve":"CVE-2026-98797","urls":{"html":"https://cve.report/CVE-2026-98797","api":"https://cve.report/api/cve/CVE-2026-98797.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-98797","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-98797"},"summary":{"title":"net: cap skb->queue_mapping when the tx queue is picked","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet: cap skb->queue_mapping when the tx queue is picked\n\nskbedit can set skb->queue_mapping and raise the per-CPU skip_txqueue\nflag so __dev_queue_xmit() honours the mapping. __dev_queue_xmit()\ncleared the flag before sch_handle_egress() and only read it afterwards,\nso the flag was not confined to the xmit that set it: a nested xmit\n(mirred redirect or mirror, or a drop after skbedit) could set the flag\nand the outer xmit would consume it for an skb that never went through\nskbedit.\n\nA forwarded packet still carries the ingress NIC's rx_queue + 1 in\nskb->queue_mapping, so the outer device then indexes its tx queue state\nwith that stale value. Taprio's child array q->qdiscs[] is sized to the\ndevice's queue count, so taprio_enqueue() indexes past its allocation\nand dereferences the result as a struct Qdisc *.\n\nWe (ab)use the skb->nf_skip_egress which means \"skip netfilter egress\nfor this packet\" to tag to \"am I in tc egress?\". Despite the overload\nI dont see it as a conflict since the marker is set only around the\nsingle sch_handle_egress() call and ingress path is guarded by\ntc_at_ingress.\nI will send a followup(net-next) patch once this hits net-next to\nrename the skb->nf_skip_egress bit/flag to skb->skip_egress\n\nArm the flag only from the egress classifier that can use it: raise\nskip_txqueue from tcf_skbedit_act() only when it runs inside\nsch_handle_egress(), thanks to skb->nf_skip_egress. An egress qdisc\nclassifier runs in q->enqueue(), after the tx queue has been picked,\nso a mapping it sets cannot affect the current packet; arming the flag\nthere only pollutes it for a later xmit. Then own the flag for the xmit\nframe the egress hook runs in: save the incoming value and clear it just\nbefore sch_handle_egress(), and restore it after the hook - on the\nconsumed (drop) path, or, in the same call that reads it, on the\nsurviving path. The save and the restores stay inside the\negress_needed_key static branch, so a packet pays for them only when\negress hooks are active (2f1e85b1aee4).\n\nStore the value netdev_cap_txqueue() selected back into skb->queue_mapping\nin netdev_tx_queue_mapping(), as netdev_core_pick_tx() already does, so\nthe skip_txqueue path never hands a later reader on the xmit path a\nmapping the device cannot serve. A store made still later in the same\nframe, by a tc BPF program attached to a transmit qdisc, is outside this\npath and is not re-capped; a separate followup will resolve that path.\n\nnetdev_xmit_skip_txqueue() returns the previous flag value so the\nsave-and-clear is one call, and a no-op stub is provided when\nCONFIG_NET_EGRESS is disabled. skb->nf_skip_egress is compiled under\nCONFIG_NET_EGRESS rather than CONFIG_NETFILTER_SKIP_EGRESS, so\nskb_at_tc_egress() is valid whenever the egress path is built.\n\nA local user in a network namespace can redirect a packet from a device\nwith more TX queues to one with fewer after setting a mapping valid only\non the larger device. That reaches these reads and, under KASAN, faults\nwith \"slab-out-of-bounds in taprio_enqueue\".\n\nConditions to recreate the bug: the report's own trigger is a local user\nwith CAP_NET_ADMIN in a network namespace, so no eBPF program is needed.\nWith CONFIG_NET_SCH_TAPRIO=y, CONFIG_NET_ACT_SKBEDIT=y,\nCONFIG_NET_ACT_MIRRED=y, CONFIG_NET_CLS_MATCHALL=y,\nCONFIG_NET_SCH_PRIO=y and KASAN enabled, create qa (3 queues), qb\n(2 queues) and qc (1 queue) as dummy devices; put a taprio root on qb\n(num_tc 1, queues 2@0) and clsact on all three; then add an egress\nmatchall filter on every device. On qa: \"action skbedit queue_mapping 2\npipe action mirred egress redirect dev qb\". On qb: \"action mirred egress\nmirror dev qc\". On qc: \"action skbedit queue_mapping 0 pipe\". Send one\npacket out qa. qc's skbedit sets the flag while qb's outer xmit is in\nflight; without the fix qb consumes it and reads its two-entry taprio\nchild array with the forwarded packet's stale mapping. A qc whose\nskb\n---truncated---","state":"PUBLISHED","assigner":"Linux","published_at":"2026-10-18 16:17:33","updated_at":"2026-10-19 10:19:43"},"problem_types":[],"metrics":[],"references":[{"url":"https://git.kernel.org/stable/c/c6ec35c8267c84c2094cb485db20c06384fc2bcc","name":"https://git.kernel.org/stable/c/c6ec35c8267c84c2094cb485db20c06384fc2bcc","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/f99de42f5c6f8d088063817dad82c3334e87c570","name":"https://git.kernel.org/stable/c/f99de42f5c6f8d088063817dad82c3334e87c570","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/ea4d4b5dddb5121e64f56fd8e0720bd8b447b63d","name":"https://git.kernel.org/stable/c/ea4d4b5dddb5121e64f56fd8e0720bd8b447b63d","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/2f581814e4e3ea6a5e98f49813dc4c68444a0c4a","name":"https://git.kernel.org/stable/c/2f581814e4e3ea6a5e98f49813dc4c68444a0c4a","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-98797","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-98797","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 2f1e85b1aee459b7d0fd981839042c6a38ffaf0c c6ec35c8267c84c2094cb485db20c06384fc2bcc git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 2f1e85b1aee459b7d0fd981839042c6a38ffaf0c 2f581814e4e3ea6a5e98f49813dc4c68444a0c4a git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 2f1e85b1aee459b7d0fd981839042c6a38ffaf0c f99de42f5c6f8d088063817dad82c3334e87c570 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 2f1e85b1aee459b7d0fd981839042c6a38ffaf0c ea4d4b5dddb5121e64f56fd8e0720bd8b447b63d git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 5.19","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 5.19 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.12.113 6.12.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.18.56 6.18.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.2.10 7.2.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.3 * original_commit_for_fix","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":null,"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"cna":{"affected":[{"defaultStatus":"unaffected","product":"Linux","programFiles":["include/linux/netfilter_netdev.h","include/linux/rtnetlink.h","include/linux/skbuff.h","include/net/sch_generic.h","net/core/dev.c","net/sched/act_skbedit.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"lessThan":"c6ec35c8267c84c2094cb485db20c06384fc2bcc","status":"affected","version":"2f1e85b1aee459b7d0fd981839042c6a38ffaf0c","versionType":"git"},{"lessThan":"2f581814e4e3ea6a5e98f49813dc4c68444a0c4a","status":"affected","version":"2f1e85b1aee459b7d0fd981839042c6a38ffaf0c","versionType":"git"},{"lessThan":"f99de42f5c6f8d088063817dad82c3334e87c570","status":"affected","version":"2f1e85b1aee459b7d0fd981839042c6a38ffaf0c","versionType":"git"},{"lessThan":"ea4d4b5dddb5121e64f56fd8e0720bd8b447b63d","status":"affected","version":"2f1e85b1aee459b7d0fd981839042c6a38ffaf0c","versionType":"git"}]},{"defaultStatus":"affected","product":"Linux","programFiles":["include/linux/netfilter_netdev.h","include/linux/rtnetlink.h","include/linux/skbuff.h","include/net/sch_generic.h","net/core/dev.c","net/sched/act_skbedit.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"status":"affected","version":"5.19"},{"lessThan":"5.19","status":"unaffected","version":"0","versionType":"semver"},{"lessThanOrEqual":"6.12.*","status":"unaffected","version":"6.12.113","versionType":"semver"},{"lessThanOrEqual":"6.18.*","status":"unaffected","version":"6.18.56","versionType":"semver"},{"lessThanOrEqual":"7.2.*","status":"unaffected","version":"7.2.10","versionType":"semver"},{"lessThanOrEqual":"*","status":"unaffected","version":"7.3","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.12.113","versionStartIncluding":"5.19","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.18.56","versionStartIncluding":"5.19","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.2.10","versionStartIncluding":"5.19","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.3","versionStartIncluding":"5.19","vulnerable":true}],"negate":false,"operator":"OR"}]}],"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet: cap skb->queue_mapping when the tx queue is picked\n\nskbedit can set skb->queue_mapping and raise the per-CPU skip_txqueue\nflag so __dev_queue_xmit() honours the mapping. __dev_queue_xmit()\ncleared the flag before sch_handle_egress() and only read it afterwards,\nso the flag was not confined to the xmit that set it: a nested xmit\n(mirred redirect or mirror, or a drop after skbedit) could set the flag\nand the outer xmit would consume it for an skb that never went through\nskbedit.\n\nA forwarded packet still carries the ingress NIC's rx_queue + 1 in\nskb->queue_mapping, so the outer device then indexes its tx queue state\nwith that stale value. Taprio's child array q->qdiscs[] is sized to the\ndevice's queue count, so taprio_enqueue() indexes past its allocation\nand dereferences the result as a struct Qdisc *.\n\nWe (ab)use the skb->nf_skip_egress which means \"skip netfilter egress\nfor this packet\" to tag to \"am I in tc egress?\". Despite the overload\nI dont see it as a conflict since the marker is set only around the\nsingle sch_handle_egress() call and ingress path is guarded by\ntc_at_ingress.\nI will send a followup(net-next) patch once this hits net-next to\nrename the skb->nf_skip_egress bit/flag to skb->skip_egress\n\nArm the flag only from the egress classifier that can use it: raise\nskip_txqueue from tcf_skbedit_act() only when it runs inside\nsch_handle_egress(), thanks to skb->nf_skip_egress. An egress qdisc\nclassifier runs in q->enqueue(), after the tx queue has been picked,\nso a mapping it sets cannot affect the current packet; arming the flag\nthere only pollutes it for a later xmit. Then own the flag for the xmit\nframe the egress hook runs in: save the incoming value and clear it just\nbefore sch_handle_egress(), and restore it after the hook - on the\nconsumed (drop) path, or, in the same call that reads it, on the\nsurviving path. The save and the restores stay inside the\negress_needed_key static branch, so a packet pays for them only when\negress hooks are active (2f1e85b1aee4).\n\nStore the value netdev_cap_txqueue() selected back into skb->queue_mapping\nin netdev_tx_queue_mapping(), as netdev_core_pick_tx() already does, so\nthe skip_txqueue path never hands a later reader on the xmit path a\nmapping the device cannot serve. A store made still later in the same\nframe, by a tc BPF program attached to a transmit qdisc, is outside this\npath and is not re-capped; a separate followup will resolve that path.\n\nnetdev_xmit_skip_txqueue() returns the previous flag value so the\nsave-and-clear is one call, and a no-op stub is provided when\nCONFIG_NET_EGRESS is disabled. skb->nf_skip_egress is compiled under\nCONFIG_NET_EGRESS rather than CONFIG_NETFILTER_SKIP_EGRESS, so\nskb_at_tc_egress() is valid whenever the egress path is built.\n\nA local user in a network namespace can redirect a packet from a device\nwith more TX queues to one with fewer after setting a mapping valid only\non the larger device. That reaches these reads and, under KASAN, faults\nwith \"slab-out-of-bounds in taprio_enqueue\".\n\nConditions to recreate the bug: the report's own trigger is a local user\nwith CAP_NET_ADMIN in a network namespace, so no eBPF program is needed.\nWith CONFIG_NET_SCH_TAPRIO=y, CONFIG_NET_ACT_SKBEDIT=y,\nCONFIG_NET_ACT_MIRRED=y, CONFIG_NET_CLS_MATCHALL=y,\nCONFIG_NET_SCH_PRIO=y and KASAN enabled, create qa (3 queues), qb\n(2 queues) and qc (1 queue) as dummy devices; put a taprio root on qb\n(num_tc 1, queues 2@0) and clsact on all three; then add an egress\nmatchall filter on every device. On qa: \"action skbedit queue_mapping 2\npipe action mirred egress redirect dev qb\". On qb: \"action mirred egress\nmirror dev qc\". On qc: \"action skbedit queue_mapping 0 pipe\". Send one\npacket out qa. qc's skbedit sets the flag while qb's outer xmit is in\nflight; without the fix qb consumes it and reads its two-entry taprio\nchild array with the forwarded packet's stale mapping. A qc whose\nskb\n---truncated---"}],"providerMetadata":{"dateUpdated":"2026-10-19T09:25:49.920Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/c6ec35c8267c84c2094cb485db20c06384fc2bcc"},{"url":"https://git.kernel.org/stable/c/2f581814e4e3ea6a5e98f49813dc4c68444a0c4a"},{"url":"https://git.kernel.org/stable/c/f99de42f5c6f8d088063817dad82c3334e87c570"},{"url":"https://git.kernel.org/stable/c/ea4d4b5dddb5121e64f56fd8e0720bd8b447b63d"}],"title":"net: cap skb->queue_mapping when the tx queue is picked","x_generator":{"engine":"bippy-1.2.0"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-98797","datePublished":"2026-10-18T15:48:41.613Z","dateReserved":"2026-09-25T10:25:14.370Z","dateUpdated":"2026-10-19T09:25:49.920Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-10-18 16:17:33","lastModifiedDate":"2026-10-19 10:19:43","problem_types":[],"metrics":[],"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"98797","Ordinal":"1","Title":"net: cap skb->queue_mapping when the tx queue is picked","CVE":"CVE-2026-98797","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"98797","Ordinal":"1","NoteData":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet: cap skb->queue_mapping when the tx queue is picked\n\nskbedit can set skb->queue_mapping and raise the per-CPU skip_txqueue\nflag so __dev_queue_xmit() honours the mapping. __dev_queue_xmit()\ncleared the flag before sch_handle_egress() and only read it afterwards,\nso the flag was not confined to the xmit that set it: a nested xmit\n(mirred redirect or mirror, or a drop after skbedit) could set the flag\nand the outer xmit would consume it for an skb that never went through\nskbedit.\n\nA forwarded packet still carries the ingress NIC's rx_queue + 1 in\nskb->queue_mapping, so the outer device then indexes its tx queue state\nwith that stale value. Taprio's child array q->qdiscs[] is sized to the\ndevice's queue count, so taprio_enqueue() indexes past its allocation\nand dereferences the result as a struct Qdisc *.\n\nWe (ab)use the skb->nf_skip_egress which means \"skip netfilter egress\nfor this packet\" to tag to \"am I in tc egress?\". Despite the overload\nI dont see it as a conflict since the marker is set only around the\nsingle sch_handle_egress() call and ingress path is guarded by\ntc_at_ingress.\nI will send a followup(net-next) patch once this hits net-next to\nrename the skb->nf_skip_egress bit/flag to skb->skip_egress\n\nArm the flag only from the egress classifier that can use it: raise\nskip_txqueue from tcf_skbedit_act() only when it runs inside\nsch_handle_egress(), thanks to skb->nf_skip_egress. An egress qdisc\nclassifier runs in q->enqueue(), after the tx queue has been picked,\nso a mapping it sets cannot affect the current packet; arming the flag\nthere only pollutes it for a later xmit. Then own the flag for the xmit\nframe the egress hook runs in: save the incoming value and clear it just\nbefore sch_handle_egress(), and restore it after the hook - on the\nconsumed (drop) path, or, in the same call that reads it, on the\nsurviving path. The save and the restores stay inside the\negress_needed_key static branch, so a packet pays for them only when\negress hooks are active (2f1e85b1aee4).\n\nStore the value netdev_cap_txqueue() selected back into skb->queue_mapping\nin netdev_tx_queue_mapping(), as netdev_core_pick_tx() already does, so\nthe skip_txqueue path never hands a later reader on the xmit path a\nmapping the device cannot serve. A store made still later in the same\nframe, by a tc BPF program attached to a transmit qdisc, is outside this\npath and is not re-capped; a separate followup will resolve that path.\n\nnetdev_xmit_skip_txqueue() returns the previous flag value so the\nsave-and-clear is one call, and a no-op stub is provided when\nCONFIG_NET_EGRESS is disabled. skb->nf_skip_egress is compiled under\nCONFIG_NET_EGRESS rather than CONFIG_NETFILTER_SKIP_EGRESS, so\nskb_at_tc_egress() is valid whenever the egress path is built.\n\nA local user in a network namespace can redirect a packet from a device\nwith more TX queues to one with fewer after setting a mapping valid only\non the larger device. That reaches these reads and, under KASAN, faults\nwith \"slab-out-of-bounds in taprio_enqueue\".\n\nConditions to recreate the bug: the report's own trigger is a local user\nwith CAP_NET_ADMIN in a network namespace, so no eBPF program is needed.\nWith CONFIG_NET_SCH_TAPRIO=y, CONFIG_NET_ACT_SKBEDIT=y,\nCONFIG_NET_ACT_MIRRED=y, CONFIG_NET_CLS_MATCHALL=y,\nCONFIG_NET_SCH_PRIO=y and KASAN enabled, create qa (3 queues), qb\n(2 queues) and qc (1 queue) as dummy devices; put a taprio root on qb\n(num_tc 1, queues 2@0) and clsact on all three; then add an egress\nmatchall filter on every device. On qa: \"action skbedit queue_mapping 2\npipe action mirred egress redirect dev qb\". On qb: \"action mirred egress\nmirror dev qc\". On qc: \"action skbedit queue_mapping 0 pipe\". Send one\npacket out qa. qc's skbedit sets the flag while qb's outer xmit is in\nflight; without the fix qb consumes it and reads its two-entry taprio\nchild array with the forwarded packet's stale mapping. A qc whose\nskb\n---truncated---","Type":"Description","Title":"net: cap skb->queue_mapping when the tx queue is picked"}]}}}