node-csv: Prototype replacement still reachable via columns path

MEDIUM 6.9CVE-2026-85063 · GHSA-8cw4-87c7-c6xx · Published 03/09/2026 · updated 09/09/2026

In short

CVE-2026-85063 is a MEDIUM (CVSS 6.9) vulnerability affecting csv-parse.
Chance of exploitation in the next 30 days (EPSS): 0.57%, higher than 47.2% of all vulnerabilities.
Fix: update to 7.0.2 or later.

Package	Affected versions	Patched versions
csv-parse npm	`< 7.0.2`	`7.0.2`

Description

Impact

With columns: true and group_columns_by_name: true, a duplicated proto header causes the duplicate-column branch to assign an array to obj['proto'], invoking the proto setter and replacing the parsed record object's prototype with attacker-controlled data. Fixed in 7.0.2 (Object.hasOwn duplicate check + Object.defineProperty assignment).

Patches

The problem been patched.

Workarounds

Disable usage of both the columns and group_columns_by_name options.

References

issue #496, PR #497

NVD description

node-csv is a full-featured CSV parser with a simple API that is tested against large datasets. Prior to 7.0.2, csv-parse with the columns and group_columns_by_name options enabled treats a duplicate __proto__ header as an existing property in packages/csv-parse/lib/api/index.js, assigns an attacker-controlled array through obj['__proto__'], and replaces the parsed record object's prototype. A malicious CSV header can therefore inject inherited array values into the returned record, hide those inherited values from JSON serialization, and affect property enumeration and type or shape checks in applications that process the record. This issue is fixed in version 7.0.2.