# GO-2026-5051: Out-of-bounds read and panic in ReadDir in github.com/cloudsoda/go-smb2 and github.com/hirochachacha/go-smb2

> A remote attacker can crash the Go SMB2 client via a malicious server response, causing a denial of service.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 27 Jul 2026

## What is GO-2026-5051?

GO-2026-5051 is a denial of service vulnerability in github.com/cloudsoda/go-smb2, published on 27 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

ReadDir and ReadDirPlus parse the QUERY_DIRECTORY SMB response by advancing through entries using the server-supplied NextEntryOffset field. The pre-fix code does not bound next against the remaining buffer before re-slicing, and the entry decoder IsInvalid check performs length arithmetic in int after narrowing from uint16.

A guest or anonymous directory listing against an attacker-controlled or man-in-the-middle SMB server crashes the Go client process with a runtime panic when the response contains an entry whose NextEntryOffset is larger than the remaining buffer, or whose declared FileNameLength produces a length that does not match the actual buffer size.

## Which versions are affected by GO-2026-5051?

2 open source packages ship an affected version, including github.com/cloudsoda/go-smb2 and github.com/hirochachacha/go-smb2.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/cloudsoda/go-smb2` | Go | All versions | 0.0.0-20260609183447-7b96c35f5f4b |
| `github.com/hirochachacha/go-smb2` | Go | All versions | None |

## How do I fix GO-2026-5051?

Upgrade github.com/cloudsoda/go-smb2 to 0.0.0-20260609183447-7b96c35f5f4b or later.

## Is GO-2026-5051 being exploited?

There is no known exploitation of GO-2026-5051 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for GO-2026-5051 and fix it if it is affected.

What it is: GO-2026-5051 is a denial of service vulnerability in github.com/cloudsoda/go-smb2, published on 27 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of GO-2026-5051 in the wild and no public exploit code.

Affected packages and fixed versions:
- github.com/cloudsoda/go-smb2 (Go): affected all versions; fixed in 0.0.0-20260609183447-7b96c35f5f4b
- github.com/hirochachacha/go-smb2 (Go): affected all versions; no fix listed

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/GO-2026-5051/ (Markdown: https://insights.sbomify.com/GO-2026-5051/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/GO-2026-5051

---
From sbomify Insights: https://insights.sbomify.com/GO-2026-5051/
Summaries are generated and may contain mistakes; the official description above is the record.