{ "schema_version": "1.6.1", "id": "RPI-CVE-2026-31469", "modified": "2026-10-09T11:39:44Z", "upstream": [ "CVE-2026-31469" ], "published": "2026-04-22T13:57:42Z", "summary": "virtio_net: Fix UAF on dst_ops when IFF_XMIT_DST_RELEASE is cleared and napi_tx is false", "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->dst 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", "severity": [ { "type": "CVSS_V3", "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H" } ], "affected": [ { "package": { "ecosystem": "Raspberry Pi OS:12", "name": "linux" }, "versions": [ "1:6.1.47-1+rpt4" ], "ecosystem_specific": { "binaries": [ { "binary_name": "linux-image-6.1.0-rpi3-rpi-2712", "binary_version": "1:6.1.47-1+rpt4" }, { "binary_name": "linux-image-6.1.0-rpi3-rpi-v6", "binary_version": "1:6.1.47-1+rpt4" }, { "binary_name": "linux-image-6.1.0-rpi3-rpi-v7", "binary_version": "1:6.1.47-1+rpt4" }, { "binary_name": "linux-image-6.1.0-rpi3-rpi-v7l", "binary_version": "1:6.1.47-1+rpt4" }, { "binary_name": "linux-image-6.1.0-rpi3-rpi-v8", "binary_version": "1:6.1.47-1+rpt4" } ] }, "database_specific": { "per_version": { "1:6.1.47-1+rpt4": { "linux_commit": "655fc658a15ae7a6f37103754adb39ba52a9a14e", "upstream_version": "6.1.47", "assessment": "commit ancestry (strak rule)", "upstream_fixed": "6.1.168", "compiled_filter": false } } } } ], "references": [ { "type": "ADVISORY", "url": "https://www.cve.org/CVERecord?id=CVE-2026-31469" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/be0e63f3b97bbaf453c542e8a15ba2a536e2ac01" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/c1ec36cb3768574b916f20d2d7415fd14fa1bf12" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/8a4790850e710fd6771e4d2112168ed1dd6c0e54" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/fedd2e1630cac920844997227ccbe7b26a76375a" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/f04733c4dc40c43899c3d1c97afbae5831a3770f" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/9a18629f2525781f0f3dda7be72b204e4cf77d08" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/63d45077b97bb0e0fe0c75931acbbca7a47af141" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/ba8bda9a0896746053aa97ac6c3e08168729172c" } ], "database_specific": { "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git", "upstream_modified": "2026-08-05T13:16:28Z", "severity": { "source": "kernel CNA", "cvss_v3_score": 7.8, "cvss_v3_severity": "High", "scenario": "AV:L - The vulnerable virtio_net transmit/free path is reached through local packet transmission plus local netlink/ethtool namespace setup on a virtio_net interface. Remote traffic alone does not provide the required control over tc/qdisc, TX NAPI state, and namespace/device lifecycle.\nAC:L - The required conditions are attacker-controllable once the attacker has the needed network administration rights: disable TX NAPI, clear IFF_XMIT_DST_RELEASE via tc route filtering, queue packets, destroy the namespace, then trigger another transmit. There is no uncontrollable race; the pending-ring timing can be induced with normal traffic.\nPR:L - The setup requires CAP_NET_ADMIN for tc/qdisc, ethtool coalescing, and net namespace/device operations. In a reasonable delegated container or network-namespace deployment with a virtio_net interface, that maps to low privileges rather than init-namespace root, and uncertainty is resolved toward higher severity.\nUI:N - No victim user action is required after the attacker has the relevant local privileges. The attacker can perform the configuration, traffic generation, namespace teardown, and retrigger steps directly.\nS:U - The bug is in the kernel networking/virtio_net path and impacts the same kernel security authority. This is not a VM escape, IOMMU bypass, or other cross-scope boundary by itself.\nC:H - This is a use-after-free involving dst_ops referenced from an skb-held dst_entry after namespace teardown. Kernel UAFs are treated as high confidentiality impact because freed object reuse can enable memory disclosure primitives.\nI:H - The stale dst_ops/percpu-counter access is memory corruption in kernel context. As a kernel UAF, it is defensibly treated as exploitable for control-flow or write-primitive development.\nA:H - The reported failure is a kernel paging request/oops in dst_release via free_old_xmit. Even without full exploitation, the UAF can crash the kernel, causing high availability impact." } } }