CVE-2023-54243 netfilter: ebtables: fix table blob use-after-free
A use-after-free vulnerability in the Linux kernel's ebtables netfilter module allows attackers to potentially execute arbitrary code or escalate privileges.
- 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-2023-54243?
CVE-2023-54243 is a high-severity use after free vulnerability in Linux, published on 30 Dec 2025. 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: ebtables: fix table blob use-after-free
We are not allowed to return an error at this point. Looking at the code it looks like ret is always 0 at this point, but its not.
t = find_table_lock(net, repl->name, &ret, &ebt_mutex);
... this can return a valid table, with ret != 0.
This bug causes update of table->private with the new blob, but then frees the blob right away in the caller.
Syzbot report:
BUG: KASAN: vmalloc-out-of-bounds in __ebt_unregister_table+0xc00/0xcd0 net/bridge/netfilter/ebtables.c:1168 Read of size 4 at addr ffffc90005425000 by task kworker/u4:4/74 Workqueue: netns cleanup_net Call Trace: kasan_report+0xbf/0x1f0 mm/kasan/report.c:517 __ebt_unregister_table+0xc00/0xcd0 net/bridge/netfilter/ebtables.c:1168 ebt_unregister_table+0x35/0x40 net/bridge/netfilter/ebtables.c:1372 ops_exit_list+0xb0/0x170 net/core/net_namespace.c:169 cleanup_net+0x4ee/0xb10 net/core/net_namespace.c:613 ...
ip(6)tables appears to be ok (ret should be 0 at this point) but make this more obvious.
Which versions are affected by CVE-2023-54243?
How do I fix CVE-2023-54243?
Apply the vendor's patch.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2023-54243 being exploited?
There is no known exploitation of CVE-2023-54243 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2023-54243, DEBIAN-CVE-2023-54243, GHSA-2hrc-j4gc-h2p8, UBUNTU-CVE-2023-54243.