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CVE-2025-38732 netfilter: nf_reject: don't leak dst refcount for loopback packets

Description

In the Linux kernel, the following vulnerability has been resolved: netfilter: nf_reject: don't leak dst refcount for loopback packets recent patches to add a WARN() when replacing skb dst entry found an old bug: WARNING: include/linux/skbuff.h:1165 skb_dst_check_unset include/linux/skbuff.h:1164 [inline] WARNING: include/linux/skbuff.h:1165 skb_dst_set include/linux/skbuff.h:1210 [inline] WARNING: include/linux/skbuff.h:1165 nf_reject_fill_skb_dst+0x2a4/0x330 net/ipv4/netfilter/nf_reject_ipv4.c:234 [..] Call Trace: nf_send_unreach+0x17b/0x6e0 net/ipv4/netfilter/nf_reject_ipv4.c:325 nft_reject_inet_eval+0x4bc/0x690 net/netfilter/nft_reject_inet.c:27 expr_call_ops_eval net/netfilter/nf_tables_core.c:237 [inline] .. This is because blamed commit forgot about loopback packets. Such packets already have a dst_entry attached, even at PRE_ROUTING stage. Instead of checking hook just check if the skb already has a route attached to it.

Affected products and versions

Product Affected versions Fixed in
Linux 6.17 earliest → < 6.17 6.17
Linux 6.16 earliest → < 6.16.4 6.16.4
Linux 6.12 earliest → < 6.12.44 6.12.44
Linux 6.6 earliest → < 6.6.103 6.6.103
Linux 6.1 earliest → < 6.1.149 6.1.149
Linux 5.15 earliest → < 5.15.190 5.15.190
Linux 5.10 earliest → < 5.10.241 5.10.241
Linux 5.9 No fix stated
SIMATIC CN 4100 5.0 earliest → < 5.0 5.0
Show the 3 other branches
Product Affected versions Fixed in
SIMATIC S7-1500 CPU 1518-4 PN/DP MFP 3.1 3.1.7 → latest No fix stated
SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP 3.1 3.1.7 → latest No fix stated
SIPLUS S7-1500 CPU 1518-4 PN/DP MFP 3.1 3.1.7 → latest No fix stated

References

Timeline

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