CVE-2024-26834: netfilter: nft_flow_offload: release dst in case direct xmit path is used

Severity: medium (CVSS 5.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.6% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2024-04-17 · updated 2026-08-04

Description

In the Linux kernel, the following vulnerability has been resolved: netfilter: nft_flow_offload: release dst in case direct xmit path is used Direct xmit does not use it since it calls dev_queue_xmit() to send packets, hence it calls dst_release(). kmemleak reports: unreferenced object 0xffff88814f440900 (size 184): comm "softirq", pid 0, jiffies 4294951896 hex dump (first 32 bytes): 00 60 5b 04 81 88 ff ff 00 e6 e8 82 ff ff ff ff .`[............. 21 0b 50 82 ff ff ff ff 00 00 00 00 00 00 00 00 !.P............. backtrace (crc cb2bf5d6): [<000000003ee17107>] kmem_cache_alloc+0x286/0x340 [<0000000021a5de2c>] dst_alloc+0x43/0xb0 [<00000000f0671159>] rt_dst_alloc+0x2e/0x190 [<00000000fe5092c9>] __mkroute_output+0x244/0x980 [<000000005fb96fb0>] ip_route_output_flow+0xc0/0x160 [<0000000045367433>] nf_ip_route+0xf/0x30 [<0000000085da1d8e>] nf_route+0x2d/0x60 [<00000000d1ecd1cb>] nft_flow_route+0x171/0x6a0 [nft_flow_offload] [<00000000d9b2fb60>] nft_flow_offload_eval+0x4e8/0x700 [nft_flow_offload] [<000000009f447dbb>] expr_call_ops_eval+0x53/0x330 [nf_tables] [<00000000072e1be6>] nft_do_chain+0x17c/0x840 [nf_tables] [<00000000d0551029>] nft_do_chain_inet+0xa1/0x210 [nf_tables] [<0000000097c9d5c6>] nf_hook_slow+0x5b/0x160 [<0000000005eccab1>] ip_forward+0x8b6/0x9b0 [<00000000553a269b>] ip_rcv+0x221/0x230 [<00000000412872e5>] __netif_receive_skb_one_core+0xfe/0x110

Affected products

Linux kernel: from 6.5 before 6.6.19; from 6.7 before 6.7.7; 6.8-rc1, 6.8-rc2, 6.8-rc3, 6.8-rc4, 6.8-rc5 — fixed in 6.6.19, 6.7.7

How to fix

Upgrade to a fixed version: Linux kernel 6.6.19, 6.7.7. Check the vendor advisory for mitigations.

References

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