# 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.

- **Severity:** High 8.2 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 28 Sep 2026
- **Updated:** 28 Sep 2026
- **Also known as:** CLEANSTART-2026-RI78049, CLEANSTART-2026-SF41732, CLEANSTART-2026-XJ53800, DEBIAN-CVE-2026-101903, ECHO-441d-f705-bc64, GHSA-c29m-xwm3-cm6r, MINI-3h4v-9p3f-phv9, MINI-6347-hw78-jhjq, MINI-6835-7crv-5335, MINI-6qqc-3m53-5xvp, MINI-7mpx-p58q-8fg7, MINI-8599-x9cg-q878, MINI-fm57-62m3-jc22, MINI-jhjw-jpqx-q67x, MINI-ppvp-v98x-9x3q, MINI-wg7v-mmhc-v4v6, ROOT-APP-NPM-CVE-2026-101903, UBUNTU-CVE-2026-101903

## 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 (Inefficient Regular Expression Complexity)

## Which versions are affected by CVE-2026-101903?

2 open source packages ship an affected version, including axios.


| Package | Ecosystem | 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.

## Is CVE-2026-101903 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-101903 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-101903 and fix it if it is affected.

What it is: 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.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-101903 exists.

Affected packages and fixed versions:
- axios (npm): affected from 1.16.1; fixed in 1.20.0
- axios (npm): affected from 1.16.1; fixed in 1.20.0

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-101903/ (Markdown: https://insights.sbomify.com/CVE-2026-101903/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-101903
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-101903
- OSV: https://osv.dev/vulnerability/CVE-2026-101903

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-101903/
Summaries are generated and may contain mistakes; the official description above is the record.