CVE-2025-38192
Status: ModifiedMedium (5.5)—
In the Linux kernel, the following vulnerability has been resolved:
net: clear the dst when changing skb protocol
A not-so-careful NAT46 BPF program can crash the kernel if it indiscriminately flips ingress packets from v4 to v6:
The output interface has a 4->6 program attached at ingress. We try to loop the multicast skb back to the sending socket. Ingress BPF runs as part of netif_rx(), pushes a valid v6 hdr and changes skb->protocol to v6. We enter ip6_rcv_core which tries to use skb_dst(). But the dst is still an IPv4 one left after IPv4 mcast output.
Clear the dst in all BPF helpers which change the protocol. Try to preserve metadata dsts, those may carry non-routing metadata.
Technical details traces, logs and code from the original report
BUG: kernel NULL pointer dereference, address: 0000000000000000
ip6_rcv_core (net/ipv6/ip6_input.c:190:20)
ipv6_rcv (net/ipv6/ip6_input.c:306:8)
process_backlog (net/core/dev.c:6186:4)
napi_poll (net/core/dev.c:6906:9)
net_rx_action (net/core/dev.c:7028:13)
do_softirq (kernel/softirq.c:462:3)
netif_rx (net/core/dev.c:5326:3)
dev_loopback_xmit (net/core/dev.c:4015:2)
ip_mc_finish_output (net/ipv4/ip_output.c:363:8)
NF_HOOK (./include/linux/netfilter.h:314:9)
ip_mc_output (net/ipv4/ip_output.c:400:5)
dst_output (./include/net/dst.h:459:9)
ip_local_out (net/ipv4/ip_output.c:130:9)
ip_send_skb (net/ipv4/ip_output.c:1496:8)
udp_send_skb (net/ipv4/udp.c:1040:8)
udp_sendmsg (net/ipv4/udp.c:1328:10)CVSS
- Version: 3.1
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- Base score: 5.5
Exploitation probability (EPSS)
- Probability of exploitation in the next 30 days: 0.19%
- Percentile among all scored CVEs: 8
- Score date: 10/6/2026
EPSS (Exploit Prediction Scoring System, FIRST) estimates how likely a vulnerability is to be exploited in the wild within 30 days. It complements CVSS (impact) and CISA KEV (confirmed exploitation).
Affected technologies (1)
CWEs
- CWE-476
References
- https://git.kernel.org/stable/c/2a3ad42a57b43145839f2f233fb562247658a6d9
- https://git.kernel.org/stable/c/98b1d8dc9a3170b2614f1e8c93854e75cdd83980
- https://git.kernel.org/stable/c/a046f183d21ab5ace5a96ece4cf9873a42f003a7
- https://git.kernel.org/stable/c/ba9db6f907ac02215e30128770f85fbd7db2fcf9
- https://git.kernel.org/stable/c/bfa4d86e130a09f67607482e988313430e38f6c4
- https://git.kernel.org/stable/c/e9994e7b9f7bbb882d13c8191731649249150d21
- https://cert-portal.siemens.com/productcert/html/ssa-019113.html
- https://cert-portal.siemens.com/productcert/html/ssa-082556.html
Raw JSON (NVD)
Show
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],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: clear the dst when changing skb protocol\n\nA not-so-careful NAT46 BPF program can crash the kernel\nif it indiscriminately flips ingress packets from v4 to v6:\n\n BUG: kernel NULL pointer dereference, address: 0000000000000000\n ip6_rcv_core (net/ipv6/ip6_input.c:190:20)\n ipv6_rcv (net/ipv6/ip6_input.c:306:8)\n process_backlog (net/core/dev.c:6186:4)\n napi_poll (net/core/dev.c:6906:9)\n net_rx_action (net/core/dev.c:7028:13)\n do_softirq (kernel/softirq.c:462:3)\n netif_rx (net/core/dev.c:5326:3)\n dev_loopback_xmit (net/core/dev.c:4015:2)\n ip_mc_finish_output (net/ipv4/ip_output.c:363:8)\n NF_HOOK (./include/linux/netfilter.h:314:9)\n ip_mc_output (net/ipv4/ip_output.c:400:5)\n dst_output (./include/net/dst.h:459:9)\n ip_local_out (net/ipv4/ip_output.c:130:9)\n ip_send_skb (net/ipv4/ip_output.c:1496:8)\n udp_send_skb (net/ipv4/udp.c:1040:8)\n udp_sendmsg (net/ipv4/udp.c:1328:10)\n\nThe output interface has a 4->6 program attached at ingress.\nWe try to loop the multicast skb back to the sending socket.\nIngress BPF runs as part of netif_rx(), pushes a valid v6 hdr\nand changes skb->protocol to v6. We enter ip6_rcv_core which\ntries to use skb_dst(). But the dst is still an IPv4 one left\nafter IPv4 mcast output.\n\nClear the dst in all BPF helpers which change the protocol.\nTry to preserve metadata dsts, those may carry non-routing\nmetadata."
},
{
"lang": "es",
"value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: net: borrar el dst al cambiar el protocolo skb Un programa BPF NAT46 no tan cuidadoso puede hacer que el kernel se bloquee si cambia indiscriminadamente los paquetes de entrada de v4 a v6: ERROR: kernel NULL pointer dereference, address: 0000000000000000 ip6_rcv_core (net/ipv6/ip6_input.c:190:20) ipv6_rcv (net/ipv6/ip6_input.c:306:8) process_backlog (net/core/dev.c:6186:4) napi_poll (net/core/dev.c:6906:9) net_rx_action (net/core/dev.c:7028:13) do_softirq (kernel/softirq.c:462:3) netif_rx (net/core/dev.c:5326:3) dev_loopback_xmit (net/core/dev.c:4015:2) ip_mc_finish_output (net/ipv4/ip_output.c:363:8) NF_HOOK (./include/linux/netfilter.h:314:9) ip_mc_output (net/ipv4/ip_output.c:400:5) dst_output (./include/net/dst.h:459:9) ip_local_out (net/ipv4/ip_output.c:130:9) ip_send_skb (net/ipv4/ip_output.c:1496:8) udp_send_skb (net/ipv4/udp.c:1040:8) udp_sendmsg (net/ipv4/udp.c:1328:10) La interfaz de salida tiene un programa 4->6 conectado en la entrada. Intentamos devolver el skb de multidifusión al socket de envío. El BPF de entrada se ejecuta como parte de netif_rx(), envía un hdr v6 válido y cambia el protocolo skb a v6. Introducimos ip6_rcv_core, que intenta usar skb_dst(). Sin embargo, el dst sigue siendo IPv4 tras la salida de mcast IPv4. Borre el dst en todos los ayudantes de BPF que cambien el protocolo. Intente conservar los dst de metadatos, ya que pueden contener metadatos no relacionados con el enrutamiento."
}
],
"lastModified": "2026-07-30T06:22:59.143",
"configurations": [
{
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