CVE-2026-101903
Received Received - Intake

Axios HTTP Client Regex Denial of Service via RFC 2397

Publication date: 2026-09-28

Last updated on: 2026-09-28

Assigner: GitHub, Inc.

Description
Axios is a promise-based HTTP client for the browser and Node.js. From 1.16.1 until 1.20.0, the RFC 2397 regular expression allows slash characters on both sides of the media-type separator. An application passes an attacker-controlled malformed data URL containing many slash characters and no comma. the JavaScript regular-expression engine explores many separator placements before rejecting the URL. Synchronous excessive backtracking can block the Node.js event loop and cause denial of service. The affected identifiers are fromDataURI, DATA_URL_PATTERN, data:. This issue is fixed in version 1.20.0.

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Meta Information

Published
2026-09-28
Last Modified
2026-09-28
Generated
2026-09-28
AI Q&A
2026-09-28
EPSS Evaluated
N/A
NVD
CVE-2026-101903
EUVD
EUVD-2026-88378

Affected Vendors & Products

Showing 5 associated CPEs
Vendor Product Version / Range
axios axios From 1.16.1 (inc) to 1.20.0 (exc)
axios axios From 1.16.1 (inc)
axios axios to 1.20.0 (inc)
axios axios From 1.16.1 (inc) to 1.20.0 (inc)
axios axios 1.20.0

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-1333 The product uses a regular expression with an inefficient, possibly exponential worst-case computational complexity that consumes excessive CPU cycles.

Attack-Flow Graph

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Executive Summary

This is a ReDoS (Regular Expression Denial of Service) vulnerability in the Axios library for Node.js affecting versions 1.16.1 to 1.20.0. A maliciously crafted data URL with excessive slashes and no comma causes the Node.js event loop to freeze due to inefficient regex parsing, leading to denial of service.

Detection Guidance

To detect this vulnerability, check if your system uses Axios versions between 1.16.1 and 1.20.0. Run 'npm list axios' in your project directory to verify the installed version. If the version falls within the affected range, the system is potentially vulnerable.

Impact Analysis

The vulnerability can make a server unresponsive for minutes even with small payloads, causing downtime. It can be exploited remotely without authentication, potentially disrupting services relying on Axios for HTTP requests.

Compliance Impact

This vulnerability primarily impacts system availability by causing denial of service through event loop blocking. It does not directly expose or leak data, so it may not directly violate GDPR or HIPAA data protection requirements. However, prolonged downtime could disrupt access to personal or health data, potentially violating availability requirements under these regulations.

Mitigation Strategies

Immediately upgrade Axios to version 1.20.0 or later using 'npm update axios'. As a temporary workaround, reject data: URLs before passing them to Axios or enforce strict URL length limits to prevent excessive backtracking.

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