CVE-2026-101903

Axios is a very common tool that web and mobile apps use to fetch data from the internet, a bit like a messenger that delivers requests and responses between your app and other services. This flaw is like handing that messenger a tangled, nonsensical address that takes it forever to figure out — while it's stuck untangling the address, it can't deliver anything else, so your whole app or site grinds to a halt. No customer data is stolen; the damage is your service becoming unavailable.

This matters to you if any website, app, or backend service you run uses the Axios library to make HTTP requests — Axios is used inside countless other tools and frameworks, so you may be affected indirectly even if you didn't choose it yourself. It only becomes a real risk if your application passes attacker-supplied input (such as a URL or link a user submits) into Axios's data-URL handling and that part of your app is reachable from the internet.

This is reachable by anyone on the internet without needing a login or any user action, and no fix requires special conditions to trigger — just a crafted link sent to an exposed endpoint. There's no confirmed active exploitation or public exploit code yet, but the issue is trivial to trigger, affects a widely-used library, and is drawing rising attention in security roundups, so it should be treated as an urgent patch item rather than something to defer.

1. Inventory all applications and services using Axios (direct or transitive dependency) via npm ls axios or lockfile scanning across your repos. 2. Confirm whether any affected code path reaches fromDataURI or processes untrusted data: URLs — check API endpoints, file-upload handlers, and anywhere user-controlled strings are passed to Axios URL parsing. 3. Upgrade Axios to 1.20.0 or later; this is a patch-level bump with no known breaking changes, so a standard dependency update and regression test should suffice. 4. If immediate upgrade isn't possible, add input validation/length limits on any data: URLs before they reach Axios, or a request timeout/worker isolation to limit event-loop blocking impact. 5. No CISA KEV listing and no confirmed exploitation to date — EPSS is low — so this is a proactive-patch priority rather than an active-incident response, but should not be deprioritized given ease of triggering and Axios's broad footprint. 6. After patching, monitor application response-time/latency metrics and error logs for anomalous event-loop stalls as a detection signal for exploitation attempts.

Weakness: CWE-1333 (Inefficient Regular Expression Complexity) enabling a synchronous ReDoS in Node.js. Attack vector: remote, unauthenticated, no user interaction required, reachable in default configuration whenever untrusted input reaches fromDataURI/DATA_URL_PATTERN. The regex permits slash characters on both sides of the media-type separator, causing exponential backtracking when given many slashes and no comma. Exploit maturity: no public PoC on record and no KEV listing; predicted exploitation likelihood is low with a flat trend. Press attention is rising (roundup coverage referencing actor ShinyHunters) but this reflects visibility, not confirmed exploitation. Fixed upstream in Axios 1.20.0; affected range is 1.16.1–1.19.x.