Update basic-ftp to 5.2.2 to patch CVE-2026-27699 path traversal

[Copilot]

basic-ftp ≤5.0.5 allows a malicious FTP server to write files outside the intended download directory via ../ sequences in LIST response filenames passed unsanitized to path.join() in downloadToDir(). Fixed in 5.2.0.

Changes

• package-lock.json: Bumped transitive dep basic-ftp 5.0.5 → 5.2.2 via npm update basic-ftp (no manifest change needed; get-uri's ^5.0.2 constraint already permits this range)

Reachability

basic-ftp is pulled in transitively via cypress → proxy-agent → get-uri → basic-ftp. No code in this repo calls downloadToDir() or any basic-ftp API directly — the vulnerable code path is not reachable. Update clears the Dependabot alert and removes the vulnerable version from the tree.

Original prompt

---

This section details the Dependabot vulnerability alert you should resolve

<alert_title>Basic FTP has Path Traversal Vulnerability in its downloadToDir() method</alert_title>
<alert_description>The basic-ftp library contains a path traversal vulnerability in the downloadToDir() method. A malicious FTP server can send directory listings with filenames containing path traversal sequences (../) that cause files to be written outside the intended download directory.

Source-to-Sink Flow

1. SOURCE: FTP server sends LIST response
└─> "-rw-r--r-- 1 user group 1024 Jan 20 12:00 ../../../etc/passwd"

2. PARSER: parseListUnix.ts:100 extracts filename
└─> file.name = "../../../etc/passwd"

3. VALIDATION: parseListUnix.ts:101 checks
└─> if (name === "." || name === "..") ❌ (only filters exact matches)
└─> "../../../etc/passwd" !== "." && !== ".." ✅ PASSES

4. SINK: Client.ts:707 uses filename directly
└─> const localPath = join(localDirPath, file.name)
└─> join("/safe/download", "../../../etc/passwd")
└─> Result: "/safe/download/../../../etc/passwd" → resolves to "/etc/passwd"

5. FILE WRITE: Client.ts:512 opens file
└─> fsOpen(localPath, "w") → writes to /etc/passwd (outside intended directory)

Vulnerable Code

File: src/Client.ts:707

protected async _downloadFromWorkingDir(localDirPath: string): Promise<void> {
await ensureLocalDirectory(localDirPath)
for (const file of await this.list()) {
const localPath = join(localDirPath, file.name) // ⚠️ VULNERABLE
// file.name comes from untrusted FTP server, no sanitization
await this.downloadTo(localPath, file.name)
}
}

Root Cause:
- Parser validation (parseListUnix.ts:101) only filters exact . or .. entries
- No sanitization of ../ sequences in filenames

• path.join() doesn't prevent traversal, fs.open() resolves paths

Impact

A malicious FTP server can:
- Write files to arbitrary locations on the client filesystem
- Overwrite critical system files (if user has write access)
- Potentially achieve remote code execution

Affected Versions

• Tested: v5.1.0
• Likely: All versions (code pattern exists since initial implementation)

Mitigation

Workaround: Do not use downloadToDir() with untrusted FTP servers.

Fix: Sanitize filenames before use:

import { basename } from 'path'

// In _downloadFromWorkingDir:
const sanitizedName = basename(file.name) // Strip path components
const localPath = join(localDirPath, sanitizedName)
```</alert_description>

<severity>critical</severity>
<identifiers>GHSA-5rq4-664w-9x2c, CVE-2026-27699</identifiers>
<package>basic-ftp</package>
<ecosystem>npm</ecosystem>
<vulnerable_versions>5.0.5</vulnerable_versions>
<patched_version>5.2.0</patched_version>
<manifest_path>package-lock.json</manifest_path>

<references>
<url>https://github.com/patrickjuchli/basic-ftp/security/advisories/GHSA-5rq4-664w-9x2c</url>
<url>https://nvd.nist.gov/vuln/detail/CVE-2026-27699</url>
<url>https://github.com/patrickjuchli/basic-ftp/commit/2a2a0e6514357b9eda07c2f8afbd3f04727a7cd9</url>
<url>https://github.com/patrickjuchli/basic-ftp/releases/tag/v5.2.0</url>
<url>https://github.com/advisories/GHSA-5rq4-664w-9x2c</url>
</references>

<task_instructions>Resolve this alert by updating the affected package to a non-vulnerable version. Prefer the lowest non-vulnerable version (see the patched_version field above) over the latest to minimize breaking changes. Include a Reachability Assessment section in the PR description. Review the alert_description field to understand which APIs, features, or configurations are affected, then search the codebase for usage of those specific items. If the vulnerable code path is reachable, explain how (which files, APIs, or call sites use the affected functionality) and note that the codebase is actively exposed to this vulnerability. If the vulnerable code path is not reachable, explain why (e.g. the affected API is never called, the vulnerable configuration is not used) and note that the update is primarily to satisfy vulnerability scanners rather than to address an active risk. If the advisory is too vague to determine reachability (e.g. 'improper input validation' with no specific API named), state that reachability could not be determined and explain why. Include a confidence level in the reachability assessment (e.g. high confidence if the advisory names a specific API and you confirmed it is or is not called, low confidence if the usage is indirect and hard to trace). If no patched version is available, check the alert_description field for a Workarounds section — the advisory may describe configuration changes or usage patterns that mitigate the vulnerability without a version update. If a workaround is available, apply it and leave a code comment referencing the advisory identifier explaining it is a temporary mitigation. If neither a patch nor a workaround is available, explain in the PR description why the ale...

</details>



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