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THREATINT
PUBLISHED

CVE-2025-38192

net: clear the dst when changing skb protocol



Description

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: 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) 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.

Reserved 2025-04-16 | Published 2025-07-04 | Updated 2025-07-04 | Assigner Linux

Product status

Default status
unaffected

6578171a7ff0c31dc73258f93da7407510abf085 before bfa4d86e130a09f67607482e988313430e38f6c4
affected

6578171a7ff0c31dc73258f93da7407510abf085 before 2a3ad42a57b43145839f2f233fb562247658a6d9
affected

6578171a7ff0c31dc73258f93da7407510abf085 before e9994e7b9f7bbb882d13c8191731649249150d21
affected

6578171a7ff0c31dc73258f93da7407510abf085 before ba9db6f907ac02215e30128770f85fbd7db2fcf9
affected

Default status
affected

4.8
affected

Any version before 4.8
unaffected

6.6.95
unaffected

6.12.35
unaffected

6.15.4
unaffected

6.16-rc2
unaffected

References

git.kernel.org/...c/bfa4d86e130a09f67607482e988313430e38f6c4

git.kernel.org/...c/2a3ad42a57b43145839f2f233fb562247658a6d9

git.kernel.org/...c/e9994e7b9f7bbb882d13c8191731649249150d21

git.kernel.org/...c/ba9db6f907ac02215e30128770f85fbd7db2fcf9

cve.org (CVE-2025-38192)

nvd.nist.gov (CVE-2025-38192)

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