CVE-2026-63889 scsi: scsi_transport_fc: Widen FPIN pname walker counter to u32
A remote attacker on the Fibre Channel fabric can cause a kernel hang by sending crafted FPIN frames that trigger an infinite loop due to an integer overflow.
- 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-2026-63889?
CVE-2026-63889 is a high-severity vulnerability in Linux kernel, published on 19 Jul 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:
scsi: scsi_transport_fc: Widen FPIN pname walker counter to u32
An adjacent Fibre Channel fabric actor that can deliver an FPIN ELS frame to an lpfc or qla2xxx Linux initiator can trigger a non-return in the generic FC transport. This is not a local userspace or IP network path; the attacker must be able to inject fabric traffic, for example as a compromised switch or fabric controller, or as a same-zone N_Port on a fabric that permits source spoofing.
The Link-Integrity and Peer-Congestion FPIN walkers used a u8 loop counter against the 32-bit on-wire pname_count field, and did not bound pname_count by the descriptor body already validated by the TLV walker. A pname_count of 256 therefore wraps the counter and keeps the loop condition true indefinitely.
Factor the shared pname_list[] walk into one helper, widen the counter to u32, and clamp pname_count against the entries that fit in the descriptor body before iterating.
Which versions are affected by CVE-2026-63889?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-63889?
Apply the vendor's patch.
Is CVE-2026-63889 being exploited?
There is no known exploitation of CVE-2026-63889 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2026-63889, DEBIAN-CVE-2026-63889, GHSA-w68f-2wrj-q4g6, ROOT-OS-UBUNTU-2204-CVE-2026-63889, UBUNTU-CVE-2026-63889.