# CVE-2026-63890: scsi: fcoe: Reject FIP descriptors with zero fip_dlen in CVL walker

> An unauthenticated adjacent attacker can cause a denial of service in the Linux kernel FCoE driver by sending a malformed FIP descriptor with zero length.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 19 Jul 2026
- **Updated:** 19 Jul 2026
- **Also known as:** BELL-CVE-2026-63890, DEBIAN-CVE-2026-63890, GHSA-9x5h-mxx6-q576, ROOT-OS-UBUNTU-2204-CVE-2026-63890, UBUNTU-CVE-2026-63890

## What is CVE-2026-63890?

CVE-2026-63890 is a denial of service vulnerability in Linux, 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: fcoe: Reject FIP descriptors with zero fip_dlen in CVL walker

drivers/scsi/fcoe/fcoe_ctlr.c::fcoe_ctlr_recv_clr_vlink() advanced the
descriptor cursor by an attacker-supplied fip_dlen without ever
requiring dlen >= sizeof(struct fip_desc) in the default branch.  The
named descriptor cases (FIP_DT_MAC, FIP_DT_NAME, FIP_DT_VN_ID) checked
their per-type minimum lengths, but a FIP_DT_NON_CRITICAL descriptor
(fip_dtype >= 128, which the standard requires receivers to silently
ignore) skipped that check entirely.

An unauthenticated L2 peer on the FCoE control VLAN could hang
fcoe_ctlr_recv_work on an fcoe, qedf, or bnx2fc initiator indefinitely
by emitting one FIP CVL frame whose single descriptor had fip_dtype ==
FIP_DT_NON_CRITICAL and fip_dlen == 0: the cursor advanced zero bytes
per iteration and the loop condition rlen >= sizeof(*desc) stayed true
forever, blocking every subsequent FIP frame on that controller.

Tighten the outer dlen guard to also reject dlen < sizeof(struct
fip_desc), so a malformed descriptor whose length cannot even cover the
descriptor header is rejected before the switch.  This is the same
lower-bound the named cases already apply and is the minimum scope that
closes the loop.

## Which versions are affected by CVE-2026-63890?


## How do I fix CVE-2026-63890?

Apply the vendor's patch.

## Is CVE-2026-63890 being exploited?

There is no known exploitation of CVE-2026-63890 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-63890 and fix it if it is affected.

What it is: CVE-2026-63890 is a denial of service vulnerability in Linux, published on 19 Jul 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-63890 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-63890/ (Markdown: https://insights.sbomify.com/CVE-2026-63890/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-63890
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-63890
- OSV: https://osv.dev/vulnerability/CVE-2026-63890

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-63890/
Summaries are generated and may contain mistakes; the official description above is the record.