CVE-2026-74715 bpf: Fix netns reference imbalance in conntrack kfuncs
A race condition in Linux kernel BPF conntrack kfuncs allows attackers to cause a kernel panic and denial of service via namespace reference imbalance.
- 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-2026-74715?
CVE-2026-74715 is a high-severity vulnerability in Linux, published on 22 Aug 2026. 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:
bpf: Fix netns reference imbalance in conntrack kfuncs
The opts argument of the BPF conntrack kfuncs can point to a shared map value. __bpf_nf_ct_lookup() and __bpf_nf_ct_alloc_entry() read opts->netns_id separately when acquiring and releasing the network namespace reference.
The reference imbalance can occur as follows:
CPU 0 CPU 1 read opts->netns_id (-1) skip get_net_ns_by_id() write opts->netns_id (id) read opts->netns_id (id) put_net(net) /* no matching get */
The reverse transition leaks the reference. Repeating the unmatched put can destroy a live namespace and crash later users.
The kernel reported:
Oops: general protection fault, probably for non-canonical address KASAN: null-ptr-deref in range [0x00000000000000e8-0x00000000000000ef] RIP: 0010:bpf_prog_test_run_xdp+0x52c/0x1700 Call Trace: __sys_bpf+0x1662/0x50c0 __x64_sys_bpf+0x73/0xb0 do_syscall_64+0xf9/0x540 entry_SYSCALL_64_after_hwframe+0x77/0x7f Kernel panic - not syncing: Fatal exception
Snapshot every input field of opts with READ_ONCE() before validating or using it. The netns_id snapshot keeps the namespace get/put pair balanced, while the other snapshots keep the remaining options from changing partway through an invocation. The individual reads can still observe an inconsistent combination during a concurrent update, but each selected field value remains stable for that invocation.
Which versions are affected by CVE-2026-74715?
How do I fix CVE-2026-74715?
Apply the vendor's patch.
Is CVE-2026-74715 being exploited?
There is no known exploitation of CVE-2026-74715 in the wild and no public exploit code.
Sources
Also known as AZL-97341, BELL-CVE-2026-74715, DEBIAN-CVE-2026-74715, GHSA-8qqv-vcf6-q7hx, UBUNTU-CVE-2026-74715.