basic-ftp: Quadratic-time CPU denial of service in Client.list() Unix directory-listing parser (RE_LINE backtracking)

Why it is Amber

• CVSS 8.2 high
• Public exploit or proof of concept referenced
• Remotely exploitable without logging in
• On your watchlist: npm

Affected packages

References

• https://github.com/advisories/GHSA-c475-qrg2-pj4r
• https://github.com/patrickjuchli/basic-ftp/security/advisories/GHSA-c475-qrg2-pj4r
• https://nvd.nist.gov/vuln/detail/CVE-2026-102990
• https://github.com/patrickjuchli/basic-ftp/commit/d0d9e07c56e519587bb50532ac6eadbb0cb0cfe9
• https://github.com/patrickjuchli/basic-ftp/releases/tag/v6.2.1
• https://github.com/advisories/GHSA-c475-qrg2-pj4r

Original 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.