CVE-2024-26857 geneve: make sure to pull inner header in geneve_rx()

High 7.3 Published 17 Apr 2024 Updated 5 Aug 2026

An attacker can trigger an uninitialized value read in the Linux kernel's GENEVE driver, potentially leaking sensitive memory contents.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Over the internet
Victim action needed: Not needed
Fix: Available

What is CVE-2024-26857?

CVE-2024-26857 is a high-severity vulnerability in Debian Debian Linux, published on 17 Apr 2024. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

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

geneve: make sure to pull inner header in geneve_rx()

syzbot triggered a bug in geneve_rx() [1]

Issue is similar to the one I fixed in commit 8d975c15c0cd ("ip6_tunnel: make sure to pull inner header in __ip6_tnl_rcv()")

We have to save skb->network_header in a temporary variable in order to be able to recompute the network_header pointer after a pskb_inet_may_pull() call.

pskb_inet_may_pull() makes sure the needed headers are in skb->head.

[1] BUG: KMSAN: uninit-value in IP_ECN_decapsulate include/net/inet_ecn.h:302 [inline] BUG: KMSAN: uninit-value in geneve_rx drivers/net/geneve.c:279 [inline] BUG: KMSAN: uninit-value in geneve_udp_encap_recv+0x36f9/0x3c10 drivers/net/geneve.c:391 IP_ECN_decapsulate include/net/inet_ecn.h:302 [inline] geneve_rx drivers/net/geneve.c:279 [inline] geneve_udp_encap_recv+0x36f9/0x3c10 drivers/net/geneve.c:391 udp_queue_rcv_one_skb+0x1d39/0x1f20 net/ipv4/udp.c:2108 udp_queue_rcv_skb+0x6ae/0x6e0 net/ipv4/udp.c:2186 udp_unicast_rcv_skb+0x184/0x4b0 net/ipv4/udp.c:2346 __udp4_lib_rcv+0x1c6b/0x3010 net/ipv4/udp.c:2422 udp_rcv+0x7d/0xa0 net/ipv4/udp.c:2604 ip_protocol_deliver_rcu+0x264/0x1300 net/ipv4/ip_input.c:205 ip_local_deliver_finish+0x2b8/0x440 net/ipv4/ip_input.c:233 NF_HOOK include/linux/netfilter.h:314 [inline] ip_local_deliver+0x21f/0x490 net/ipv4/ip_input.c:254 dst_input include/net/dst.h:461 [inline] ip_rcv_finish net/ipv4/ip_input.c:449 [inline] NF_HOOK include/linux/netfilter.h:314 [inline] ip_rcv+0x46f/0x760 net/ipv4/ip_input.c:569 __netif_receive_skb_one_core net/core/dev.c:5534 [inline] __netif_receive_skb+0x1a6/0x5a0 net/core/dev.c:5648 process_backlog+0x480/0x8b0 net/core/dev.c:5976 __napi_poll+0xe3/0x980 net/core/dev.c:6576 napi_poll net/core/dev.c:6645 [inline] net_rx_action+0x8b8/0x1870 net/core/dev.c:6778 __do_softirq+0x1b7/0x7c5 kernel/softirq.c:553 do_softirq+0x9a/0xf0 kernel/softirq.c:454 __local_bh_enable_ip+0x9b/0xa0 kernel/softirq.c:381 local_bh_enable include/linux/bottom_half.h:33 [inline] rcu_read_unlock_bh include/linux/rcupdate.h:820 [inline] __dev_queue_xmit+0x2768/0x51c0 net/core/dev.c:4378 dev_queue_xmit include/linux/netdevice.h:3171 [inline] packet_xmit+0x9c/0x6b0 net/packet/af_packet.c:276 packet_snd net/packet/af_packet.c:3081 [inline] packet_sendmsg+0x8aef/0x9f10 net/packet/af_packet.c:3113 sock_sendmsg_nosec net/socket.c:730 [inline] __sock_sendmsg net/socket.c:745 [inline] __sys_sendto+0x735/0xa10 net/socket.c:2191 __do_sys_sendto net/socket.c:2203 [inline] __se_sys_sendto net/socket.c:2199 [inline] __x64_sys_sendto+0x125/0x1c0 net/socket.c:2199 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xcf/0x1e0 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x63/0x6b

Uninit was created at: slab_post_alloc_hook mm/slub.c:3819 [inline] slab_alloc_node mm/slub.c:3860 [inline] kmem_cache_alloc_node+0x5cb/0xbc0 mm/slub.c:3903 kmalloc_reserve+0x13d/0x4a0 net/core/skbuff.c:560 __alloc_skb+0x352/0x790 net/core/skbuff.c:651 alloc_skb include/linux/skbuff.h:1296 [inline] alloc_skb_with_frags+0xc8/0xbd0 net/core/skbuff.c:6394 sock_alloc_send_pskb+0xa80/0xbf0 net/core/sock.c:2783 packet_alloc_skb net/packet/af_packet.c:2930 [inline] packet_snd net/packet/af_packet.c:3024 [inline] packet_sendmsg+0x70c2/0x9f10 net/packet/af_packet.c:3113 sock_sendmsg_nosec net/socket.c:730 [inline] __sock_sendmsg net/socket.c:745 [inline] __sys_sendto+0x735/0xa10 net/socket.c:2191 __do_sys_sendto net/socket.c:2203 [inline] __se_sys_sendto net/socket.c:2199 [inline] __x64_sys_sendto+0x125/0x1c0 net/socket.c:2199 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xcf/0x1e0 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x63/0x6b

Weakness: CWE-908

Which versions are affected by CVE-2024-26857?

It affects 2 products.

Products include Debian Debian Linux, Linux kernel.

How do I fix CVE-2024-26857?

Apply the vendor's patch.

Is CVE-2024-26857 being exploited?

There is no known exploitation of CVE-2024-26857 in the wild and no public exploit code.

All Debian Debian Linux vulnerabilities

Sources

Also known as BELL-CVE-2024-26857, DEBIAN-CVE-2024-26857, GHSA-q8qv-35px-5j77, UBUNTU-CVE-2024-26857.