GHSA-cph5-m8f7-6c5x CVE-2021-3749

axios Inefficient Regular Expression Complexity vulnerability

High npm

Severity: 7.5 / 10; High · CVSS 3.1
Exploit chance (EPSS): 8.52%; Chance of exploitation in the next 30 days. Higher than 95.04% of scored vulnerabilities.
Known exploited: No; Not in CISA's catalog
Weakness: CWE-1333 Inefficient Regular Expression Complexity; CWE-400 Uncontrolled Resource Consumption
Fix: 0.21.2; Upgrade axios to this version or later

Description

axios before v0.21.2 is vulnerable to Inefficient Regular Expression Complexity.

Affected versions

npm

Package	Vulnerable	Fixed in
axios	`< 0.21.2`	`0.21.2`

How to fix

Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.

axios npm → `0.21.2`

npm

npm install axios@0.21.2

yarn

yarn add axios@0.21.2

pnpm

pnpm add axios@0.21.2

Severity breakdown

CVSS 3.1 7.5

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack vector: Network
Attack complexity: Low
Privileges required: None
User interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: None
Availability: High

Weakness

CWE-1333: Inefficient Regular Expression Complexity

The product uses a regular expression with a worst-case computational complexity that is inefficient and possibly exponential.

How to prevent it

Architecture and Design: Use regular expressions that do not support backtracking, e.g. by removing nested quantifiers.
System Configuration: Set backtracking limits in the configuration of the regular expression implementation, such as PHP's pcre.backtrack_limit. Also consider limits on execution time for the process.
Implementation: Do not use regular expressions with untrusted input. If regular expressions must be used, avoid using backtracking in the expression.
Implementation: Limit the length of the input that the regular expression will process.

CWE-400: Uncontrolled Resource Consumption

The product does not properly control the allocation and maintenance of a limited resource.

How to prevent it

Architecture and Design: Design throttling mechanisms into the system architecture. The best protection is to limit the amount of resources that an unauthorized user can cause to be expended. A strong authentication and access control model will help prevent such attacks from occurring in the first place. The login application should be protected against DoS attacks as much as possible. Limiting the database access, perhaps by caching result sets, can help minimize the resources expended. To further limit the potential for a DoS attack, consider tracking the rate of requests received from users and blocking requests that exceed a defined rate threshold.
Architecture and Design: Mitigation of resource exhaustion attacks requires that the target system either: recognizes the attack and denies that user further access for a given amount of time, or uniformly throttles all requests in order to make it more difficult to consume resources more quickly than they can again be freed. The first of these solutions is an issue in itself though, since it may allow attackers to prevent the use of the system by a particular valid user. If the attacker impersonates the valid user, they may be able to prevent the user from accessing the server in question. The second solution is simply difficult to effectively institute -- and even when properly done, it does not provide a full solution. It simply makes the attack require more resources on the part of the attacker.
Architecture and Design: Ensure that protocols have specific limits of scale placed on them.
Implementation: Ensure that all failures in resource allocation place the system into a safe posture.

References

Advisories

nvd.nist.gov/vuln/detail/CVE-2021-3749

Packages

github.com/axios/axios

Timeline

Sep 1, 2021 Published
Sep 10, 2026 Last updated by the source
Nov 1, 2026 Latest EPSS score

Advisory	Severity	Why it's related
GHSA-44g4-m2mj-wpvx Axios: CIDR-form NO_PROXY entries are ignored, causing proxy exclusion bypass for internal IP ranges	Medium	Also affects axios
GHSA-x97p-jq2g-jp4f Axios: Prototype Pollution Gadget in axios toFormData Options	High	Also affects axios
GHSA-vh66-26gq-q6x8 Axios: Prototype pollution gadget in fetch adapter can alter outbound requests	Medium	Also affects axios
GHSA-r4gj-5m52-g5wh Axios: maxRedirects: 0 is not enforced by the fetch adapter, allowing redirect-based SSRF	High	Also affects axios
GHSA-mghh-pgcx-3jjj Axios: ReDoS (O(N²)) in shouldBypassProxy host normalization, reachable via untrusted redirect Location	High	Also affects axios
GHSA-m8m8-qj5v-23w3 Axios: Node HTTP adapter prototype-pollution gadget allows request socket hijack via inherited createConnection	High	Also affects axios
GHSA-j8rh-479h-cp32 Axios: Header Injection via Inherited headers After Minimal Interceptor	Medium	Also affects axios
GHSA-c29m-xwm3-cm6r Axios: ReDoS in fromDataURI data: URL parser freezes the Node event loop (DoS)	High	Also affects axios

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