CVE-2026-98277 eth: fbnic: ring the doorbell if a burst ends in a drop
A missing doorbell ring in the fbnic driver can cause network transmission stalls and denial of service when packet bursts end in drops.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-98277?
CVE-2026-98277 is a denial of service vulnerability in Linux, published on 6 Oct 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:
eth: fbnic: ring the doorbell if a burst ends in a drop
fbnic_tx_map() skips the doorbell write, and the completion request, for every packet handed to it with xmit_more set, counting on the packet which ends the burst to publish them all. When that packet is dropped instead - skb_put_padto(), skb_cow_head() or a DMA mapping failure - nothing rings. The descriptors of the preceding packets stay invisible to the HW until the next transmit on that queue, which for a burst-then-idle workload may never come.
Remember the meta descriptor of the last packet left without a doorbell and flush it from the error paths. The completion request has to be set on that descriptor rather than simply writing the tail, otherwise the HW would transmit the packets but never report a head, and the ring would fill up and stall for good.
This is very similar to Joe's recent series of fixes for bnxt. Not seen in real life, reproduced under QEMU with failure injection.
Which versions are affected by CVE-2026-98277?
How do I fix CVE-2026-98277?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-98277 being exploited?
There is no known exploitation of CVE-2026-98277 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-98277, DEBIAN-CVE-2026-98277, GHSA-xjm7-64jw-75jr, UBUNTU-CVE-2026-98277.