# CVE-2026-31537: smb: server: make use of smbdirect_socket.send_io.bcredits

> A flaw in the Linux kernel SMB server causes data stream corruption during immediate sends, potentially leading to denial of service.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H`)
- **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:** Yes
- **Published:** 24 Apr 2026
- **Updated:** 11 May 2026
- **Also known as:** BELL-CVE-2026-31537, DEBIAN-CVE-2026-31537, GHSA-2996-rjmh-m244, ROOT-OS-DEBIAN-12-CVE-2026-31537, ROOT-OS-DEBIAN-13-CVE-2026-31537, ROOT-OS-UBUNTU-2204-CVE-2026-31537, ROOT-OS-UBUNTU-2404-CVE-2026-31537, UBUNTU-CVE-2026-31537

## What is CVE-2026-31537?

CVE-2026-31537 is a medium-severity denial of service vulnerability in Linux kernel, published on 24 Apr 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:

smb: server: make use of smbdirect_socket.send_io.bcredits

It turns out that our code will corrupt the stream of
reassabled data transfer messages when we trigger an
immendiate (empty) send.

In order to fix this we'll have a single 'batch' credit per
connection. And code getting that credit is free to use
as much messages until remaining_length reaches 0, then
the batch credit it given back and the next logical send can
happen.

## Which versions are affected by CVE-2026-31537?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-31537?

Apply the vendor's patch.

## Is CVE-2026-31537 being exploited?

There is no known exploitation of CVE-2026-31537 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-31537 and fix it if it is affected.

What it is: CVE-2026-31537 is a medium-severity denial of service vulnerability in Linux kernel, published on 24 Apr 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-2026-31537 in the wild and no public exploit code.

Affected product: Linux kernel. 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-2026-31537/ (Markdown: https://insights.sbomify.com/CVE-2026-31537/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-31537
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-31537
- OSV: https://osv.dev/vulnerability/CVE-2026-31537

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-31537/
Summaries are generated and may contain mistakes; the official description above is the record.