CVE-2026-101903 Axios: ReDoS in fromDataURI data: URL parser freezes the Node event loop (DoS)
An attacker can cause a denial of service by sending a malformed data URL that triggers excessive backtracking in the Axios library's parser.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-101903?
CVE-2026-101903 is a high-severity denial of service vulnerability in axios, published on 28 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Weakness: CWE-1333
Which versions are affected by CVE-2026-101903?
2 open source packages ship an affected version, including axios.
| Package | Affected | Fixed in |
|---|---|---|
axios npm | From 1.16.1 | 1.20.0 |
axios npm | From 1.16.1 | 1.20.0 |
How do I fix CVE-2026-101903?
Upgrade axios to 1.20.0 or later.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-101903 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-101903 exists.
Sources
Also known as CLEANSTART-2026-RI78049, CLEANSTART-2026-SF41732, CLEANSTART-2026-XJ53800, DEBIAN-CVE-2026-101903, ECHO-441d-f705-bc64, GHSA-c29m-xwm3-cm6r and 12 more.