CVE-2021-3749 Inefficient Regular Expression Complexity in axios/axios
An attacker can cause a denial of service in applications using the axios library by sending specially crafted input that triggers inefficient regular expression processing.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2021-3749?
CVE-2021-3749 is a high-severity denial of service vulnerability in axios/axios, published on 31 Aug 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
axios is vulnerable to Inefficient Regular Expression Complexity
Which versions are affected by CVE-2021-3749?
2 open source packages ship an affected version, including axios. It affects 3 products.
| Package | Affected | Fixed in |
|---|---|---|
axios npm | All versions | 0.21.2 |
axios npm | All versions | 0.21.2 |
Products include Axios Axios, Oracle Goldengate, Siemens Sinec Ins.
How do I fix CVE-2021-3749?
Upgrade axios to 0.21.2 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-2021-3749 being exploited?
There is no known exploitation of CVE-2021-3749 in the wild and no public exploit code.
Public exploit code: 1 proofs of concept on GitHub.
Other vulnerabilities in axios/axios
- CVE-2026-44494 Axios: Full Man-in-the-Middle via Prototype Pollution Gadget in `config.proxy`
- CVE-2026-44492 axios's shouldBypassProxy does not recognize IPv4-mapped IPv6 addresses, allowing NO_PROXY bypass (incomplete fix for CVE-2025-62718)
- CVE-2026-67320 axios before 0.33.0 Prototype Pollution via Node HTTP adapter
- CVE-2026-44487 Axios: Proxy-Authorization Credential Leak to Origin Server Across HTTP-to-HTTPS Redirect in Axios Node.js HTTP Adapter
- CVE-2025-27152 Possible SSRF and Credential Leakage via Absolute URL in axios Requests
Sources
Also known as DEBIAN-CVE-2021-3749, GHSA-cph5-m8f7-6c5x, ROOT-APP-NPM-CVE-2021-3749, UBUNTU-CVE-2021-3749.