Axios: ReDoS in fromDataURI data: URL parser freezes the Node event loop (DoS)

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

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 · score source

EPSS

• CVE-2026-101903: 0.44% estimated exploitation activity in the next 30 days; percentile 37.91 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary Axios for Node.js parses data: URLs in lib/helpers/fromDataURI.js. The current RFC-2397 parser uses a regular expression whose media type groups allow / inside both sides of the type/subtype match. A malformed data: URL containing many slashes and no comma forces the JavaScript regex engine to try many possible placements for the separator before failing. Applications are affected when they pass untrusted URL strings to axios and do not reject or constrain data: URLs before axios parses them. Impact An attacker can make the Node.js event loop spend significant synchronous CPU time parsing a single malformed URL. In a server that accepts a URL from an HTTP request and calls axios.get(url), this can block unrelated requests and health checks until parsing completes. The issue is availability-only. It does not disclose data or modify requests. Affected Functionality Affected: - Node.js HTTP adapter data URL handling. - axios.get() or equivalent calls where config.url has the…

Published by the source

30 Sep 2026, 15:03 UTC

Last modified by the source

30 Sep 2026, 15:15 UTC

Source last checked

26 Oct 2026, 13:06 UTC

1. Revision 4 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-c29m-xwm3-cm6r

2. Revision 3 · amended · 24 Oct 2026

   Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

3. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GHSA-c29m-xwm3-cm6r

4. Revision 1 · created · 23 Oct 2026

   Published from ghsa record GHSA-c29m-xwm3-cm6r

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# Patch Next advisory brief: CVE-2026-101903

Advisory: Axios: ReDoS in fromDataURI data: URL parser freezes the Node event loop (DoS)
IDs: CVE-2026-101903, GHSA-c29m-xwm3-cm6r
Record: https://patchnext.com/advisories/cve-2026-101903 (revision 4, source checked 26 Oct 2026, 13:06 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.2)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: axios 1.20.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm axios: affected >= 1.16.1, < 1.20.0; fixed in 1.20.0

## Suggested inspection (read-only)
- `npm ls axios --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on axios.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-c29m-xwm3-cm6r (GitHub-reviewed advisory GHSA-c29m-xwm3-cm6r lists affected ranges: npm axios >=1.16.1 <1.20.0)
- Verified: https://osv.dev/vulnerability/GHSA-c29m-xwm3-cm6r (OSV record GHSA-c29m-xwm3-cm6r lists affected ranges: npm axios >=1.16.1 <1.20.0 (fixed))

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