vulnerability / NVI-00012960 / Revision 2
basic-ftp: Quadratic-time CPU denial of service in Client.list() Unix directory-listing parser (RE_LINE backtracking)
GitHub lists this reviewed advisory for basic-ftp. Published version ranges and source prerequisites are shown below; this is not an inspection of a visitor’s application.
This report has not inspected your inventory, configuration, deployed build, reachability or evidence. A catalog listing and a severity score do not establish exposure or compromise.
01 / Meaning
Why it matters
Published affected context helps an owner decide what evidence to gather. This report has not examined your application.
8.2 HIGH (4.0)
security-advisories@github.com severity; no combined Null risk score.
02 / Applicability
The affected context
Affected versions, configuration prerequisites and known exclusions are public. Confirm each one against the deployed service.
basic-ftp
source listed<= 6.2.0
## Summary `Client.list()` parses the server's directory listing with the Unix-style parser in `parseListUnix.js`. Its `RE_LINE` regex has two adjacent `(\S+(?:\s\S+)*)` groups (owner name, then group name) followed by a required numeric size group. When a line starts with a valid listing prefix but the tokens after it never satisfy the size and date fields, the engine backtracks over every way of splitting those tokens between the two groups before it can fail, so matching one line costs roughly O(n²) in the line's length. The server whose directory a client lists controls that listing, so it can return one line that pins the Node.js event loop for as long as it likes. `parseList()` picks the parser from the last non-blank line only, then runs it on every line, so a normal line placed last selects the Unix parser and a crafted line earlier hits the quadratic match. ## Proof of concept `npm i basic-ftp && node repro.js`: ```js const net = require("net"), ftp = require("basic-ftp"); const KB = Number(process.env.LINE_KB || 128); const payload = "-rw-r--r-- 1 " + "a ".repeat((KB * 1024 - 13) / 2) + "!"; const listing = payload + "\r\n-rw-r--r-- 1 owner group 42 Jan 1 2020 file.t
03 / Response
What to do next
- investigate
Identify the exact component and deployed version, examine the linked publisher’s conditions, and retain evidence of any mitigation.
Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system. NIST National Vulnerability Database
A fixed release is not deployment evidence.
Check current vendor support and compatibility. After making a change, verify the deployed build and relevant runtime conditions. Keep the evidence, owner and time. An updated lockfile alone does not prove what is running.
04 / Limits
What this report cannot establish
- Customer inventory, deployment, reachability and exploitation have not been inspected.
- NVD lastModified does not establish freshness of every associated CPE record.
05 / Provenance
Sources you can inspect
Each assertion retains its source. Mirrored records may repeat one underlying publisher; additional links are not independent corroboration.
- GHSA-c475-qrg2-pj4r ↗
GitHub Advisory Database · vendor advisory
Observed . GitHub Advisory Database; CC-BY-4.0. Each advisory links its original attribution. Null normalizes fields.
- CVE-2026-102990 ↗
NIST National Vulnerability Database · official catalog
Observed . This product uses data from the NVD API but is not endorsed or certified by the NVD.
Public revision history
Only published revisions appear here. Routine fetches do not create a material-change event.
- Revision 2 ·
Source facts changed; compare the preserved prior revision.
- Revision 1 ·
First indexed by Null; source disclosure date is shown separately.