CVE-2024-35839 netfilter: bridge: replace physindev with physinif in nf_bridge_info
A use-after-free or null dereference in the Linux kernel netfilter bridge module can cause a system crash when processing ARP queues.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2024-35839?
CVE-2024-35839 is a high-severity vulnerability in Linux kernel, published on 17 May 2024. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
netfilter: bridge: replace physindev with physinif in nf_bridge_info
An skb can be added to a neigh->arp_queue while waiting for an arp reply. Where original skb's skb->dev can be different to neigh's neigh->dev. For instance in case of bridging dnated skb from one veth to another, the skb would be added to a neigh->arp_queue of the bridge.
As skb->dev can be reset back to nf_bridge->physindev and used, and as there is no explicit mechanism that prevents this physindev from been freed under us (for instance neigh_flush_dev doesn't cleanup skbs from different device's neigh queue) we can crash on e.g. this stack:
arp_process neigh_update skb = __skb_dequeue(&neigh->arp_queue) neigh_resolve_output(..., skb) ... br_nf_dev_xmit br_nf_pre_routing_finish_bridge_slow skb->dev = nf_bridge->physindev br_handle_frame_finish
Let's use plain ifindex instead of net_device link. To peek into the original net_device we will use dev_get_by_index_rcu(). Thus either we get device and are safe to use it or we don't get it and drop skb.
Which versions are affected by CVE-2024-35839?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2024-35839?
Apply the vendor's patch.
Is CVE-2024-35839 being exploited?
There is no known exploitation of CVE-2024-35839 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-67737, BELL-CVE-2024-35839, DEBIAN-CVE-2024-35839, GHSA-gw6v-2949-7c2m, ROOT-OS-DEBIAN-11-CVE-2024-35839, ROOT-OS-UBUNTU-2204-CVE-2024-35839 and 1 more.