CVE-2026-31469

Estado: ModificadaAlta (7.8)—

In the Linux kernel, the following vulnerability has been resolved:

virtio_net: Fix UAF on dst_ops when IFF_XMIT_DST_RELEASE is cleared and napi_tx is false

A UAF issue occurs when the virtio_net driver is configured with napi_tx=N and the device's IFF_XMIT_DST_RELEASE flag is cleared (e.g., during the configuration of tc route filter rules).

When IFF_XMIT_DST_RELEASE is removed from the net_device, the network stack expects the driver to hold the reference to skb->dst until the packet is fully transmitted and freed. In virtio_net with napi_tx=N, skbs may remain in the virtio transmit ring for an extended period.

Leer descripción completaMostrar menos

If the network namespace is destroyed while these skbs are still pending, the corresponding dst_ops structure has freed. When a subsequent packet is transmitted, free_old_xmit() is triggered to clean up old skbs. It then calls dst_release() on the skb associated with the stale dst_entry. Since the dst_ops (referenced by the dst_entry) has already been freed, a UAF kernel paging request occurs.

fix it by adds skb_dst_drop(skb) in start_xmit to explicitly release the dst reference before the skb is queued in virtio_net.

Reproduction Steps: NETDEV="enp3s0"

config_qdisc_route_filter

test_ns sleep 2 test_ns

Detalles técnicos trazas, registros y código del informe original

Call Trace:
 Unable to handle kernel paging request at virtual address ffff80007e150000
 CPU: 2 UID: 0 PID: 6236 Comm: ping Kdump: loaded Not tainted 7.0.0-rc1+ #6 PREEMPT
  ...
  percpu_counter_add_batch+0x3c/0x158 lib/percpu_counter.c:98 (P)
  dst_release+0xe0/0x110  net/core/dst.c:177
  skb_release_head_state+0xe8/0x108 net/core/skbuff.c:1177
  sk_skb_reason_drop+0x54/0x2d8 net/core/skbuff.c:1255
  dev_kfree_skb_any_reason+0x64/0x78 net/core/dev.c:3469
  napi_consume_skb+0x1c4/0x3a0 net/core/skbuff.c:1527
  __free_old_xmit+0x164/0x230  drivers/net/virtio_net.c:611 [virtio_net]
  free_old_xmit drivers/net/virtio_net.c:1081 [virtio_net]
  start_xmit+0x7c/0x530 drivers/net/virtio_net.c:3329 [virtio_net]
  ...

config_qdisc_route_filter() {
    tc qdisc del dev $NETDEV root
    tc qdisc add dev $NETDEV root handle 1: prio
    tc filter add dev $NETDEV parent 1:0 \
	protocol ip prio 100 route to 100 flowid 1:1
    ip route add 192.168.1.100/32 dev $NETDEV realm 100
}

test_ns() {
    ip netns add testns
    ip link set $NETDEV netns testns
    ip netns exec testns ifconfig $NETDEV  10.0.32.46/24
    ip netns exec testns ping -c 1 10.0.32.1
    ip netns del testns
}

CVSS

Versión: 3.1
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Puntuación base: 7.8

Probabilidad de explotación (EPSS)

Probabilidad de explotación en los próximos 30 días: 0.18%
Percentil entre todas las CVEs puntuadas: 7
Fecha de la puntuación: 5/10/2026

EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).

🎯 Técnicas ATT&CK

Cómo se explota esta vulnerabilidad y qué consigue el atacante, en el lenguaje de MITRE ATT&CK.

ExplotaciónT1068 Exploitation for Privilege Escalationprivilege escalation75 %
Impacto principalT1499.004 Application or System Exploitationimpact65 %

Vulnerabilidad de Use-After-Free (CWE-416) en kernel Linux con acceso local privilegiado (AV:L/PR:L) sin interacción. Causaimpacto de DoS (kernel panic/paging request) al liberar referencias de memoria en operaciones de transmisión de paquetes.

Inferido por nuestro agente de análisis a partir de la descripción oficial, el vector CVSS y la CWE, y comprobado por un supervisor. Puede contener errores.

🛡️ Mitigaciones ATT&CK que cubren estas técnicas

Threat Intelligence Program Filter Network Traffic Execution Prevention Application Isolation and Sandboxing Exploit Protection Update Software

Tecnologías afectadas (1)

Linux — Linux Kernel

CWE

CWE-416

Referencias

JSON original (NVD)

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          "value": "CWE-416"
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    {
      "lang": "en",
      "value": "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"
    }
  ],
  "lastModified": "2026-07-14T13:18:42.810",
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