{"id":"AZL-83264","summary":"CVE-2026-31469 affecting package kernel for versions less than 6.6.134.1-2","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nvirtio_net: Fix UAF on dst_ops when IFF_XMIT_DST_RELEASE is cleared and napi_tx is false\n\nA UAF issue occurs when the virtio_net driver is configured with napi_tx=N\nand the device's IFF_XMIT_DST_RELEASE flag is cleared\n(e.g., during the configuration of tc route filter rules).\n\nWhen IFF_XMIT_DST_RELEASE is removed from the net_device, the network stack\nexpects the driver to hold the reference to skb-\u003edst until the packet\nis fully transmitted and freed. In virtio_net with napi_tx=N,\nskbs may remain in the virtio transmit ring for an extended period.\n\nIf the network namespace is destroyed while these skbs are still pending,\nthe corresponding dst_ops structure has freed. When a subsequent packet\nis transmitted, free_old_xmit() is triggered to clean up old skbs.\nIt then calls dst_release() on the skb associated with the stale dst_entry.\nSince the dst_ops (referenced by the dst_entry) has already been freed,\na UAF kernel paging request occurs.\n\nfix it by adds skb_dst_drop(skb) in start_xmit to explicitly release\nthe dst reference before the skb is queued in virtio_net.\n\nCall Trace:\n Unable to handle kernel paging request at virtual address ffff80007e150000\n CPU: 2 UID: 0 PID: 6236 Comm: ping Kdump: loaded Not tainted 7.0.0-rc1+ #6 PREEMPT\n  ...\n  percpu_counter_add_batch+0x3c/0x158 lib/percpu_counter.c:98 (P)\n  dst_release+0xe0/0x110  net/core/dst.c:177\n  skb_release_head_state+0xe8/0x108 net/core/skbuff.c:1177\n  sk_skb_reason_drop+0x54/0x2d8 net/core/skbuff.c:1255\n  dev_kfree_skb_any_reason+0x64/0x78 net/core/dev.c:3469\n  napi_consume_skb+0x1c4/0x3a0 net/core/skbuff.c:1527\n  __free_old_xmit+0x164/0x230  drivers/net/virtio_net.c:611 [virtio_net]\n  free_old_xmit drivers/net/virtio_net.c:1081 [virtio_net]\n  start_xmit+0x7c/0x530 drivers/net/virtio_net.c:3329 [virtio_net]\n  ...\n\nReproduction Steps:\nNETDEV=\"enp3s0\"\n\nconfig_qdisc_route_filter() {\n    tc qdisc del dev $NETDEV root\n    tc qdisc add dev $NETDEV root handle 1: prio\n    tc filter add dev $NETDEV parent 1:0 \\\n\tprotocol ip prio 100 route to 100 flowid 1:1\n    ip route add 192.168.1.100/32 dev $NETDEV realm 100\n}\n\ntest_ns() {\n    ip netns add testns\n    ip link set $NETDEV netns testns\n    ip netns exec testns ifconfig $NETDEV  10.0.32.46/24\n    ip netns exec testns ping -c 1 10.0.32.1\n    ip netns del testns\n}\n\nconfig_qdisc_route_filter\n\ntest_ns\nsleep 2\ntest_ns","modified":"2026-08-28T17:47:43.656073452Z","published":"2026-04-22T14:16:43Z","upstream":["CVE-2026-31469"],"references":[{"type":"WEB","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-31469"}],"affected":[{"package":{"name":"kernel","ecosystem":"Azure Linux:3","purl":"pkg:rpm/azure-linux/kernel"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.6.134.1-2"}]}],"database_specific":{"source":"https://github.com/microsoft/AzureLinuxVulnerabilityData/blob/main/osv/AZL-83264.json"}}],"schema_version":"1.9.0"}