CVE-2026-39865

A vulnerability in the axios library allows sending requests to absolute URLs instead of relative ones, potentially leading to SSRF attacks and credential leakage. Even with baseURL set, axios ignores it and sends the request to the specified absolute URL.

Axios versions 0.28.0 and later contain uncontrolled recursion in formDataToJSON, the helper behind the public axios.formToJSON() / named formToJSON API and the default request transform used when FormData is sent with an application/json content type.

Axios is vulnerable to read-side prototype-pollution gadgets when Object.prototype has already been polluted by another vulnerability or dependency. The most broadly reachable issue is in the bodyless method aliases: axios.get(), axios.delete(), axios.head(), and axios.options().

Axios can consume inherited properties from nested request option objects when the JavaScript process already has a polluted Object.prototype. The top-level merged config is protected with a null prototype, but nested plain objects such as auth and paramsSerializer are cloned into objects with a prototype.

An issue in Axios 1.5.1 inadvertently reveals the confidential XSRF-TOKEN stored in cookies by including it in the HTTP header X-XSRF-TOKEN for every request made to any host, allowing attackers to view sensitive information.

Axios versions starting with 0.28.0 contain uncontrolled recursion in formDataToJSON, which is exposed as axios.formToJSON() and used internally when axios serialises FormData with Content-Type: application/json. If an application passes attacker-controlled FormData field names, it can lead to stack exhaustion.

A vulnerability in Axios prior to versions 1.15.0 and 0.31.0 incorrectly handles hostname normalization when checking NO_PROXY rules. Requests to loopback addresses like localhost. (with a trailing dot) or [::1] (IPv6 literal) skip NO_PROXY matching and go through the configured proxy.

Axios versions 1.15.0 through 1.20.0 incorrectly treat NO_PROXY CIDR entries as textual hostname suffixes instead of network ranges. A request to an address covered by a CIDR entry in NO_PROXY is not matched and is sent through the configured proxy. For plaintext HTTP the proxy can observe and modify URLs, headers, and bodies; for HTTPS it can observe connection metadata and CONNECT requests.

Axios from 0.28.0 until 0.34.0 and 1.15.1 until 1.20.0 processes inherited serialization options and visitor properties supplied through prototype pollution. A separate same-process prototype-pollution flaw supplies inherited dots, indexes, metaTokens, maxDepth, visitor, or Blob values before object serialization. The inherited options alter toFormData field naming and data interpretation, maxDepth can force request failure, Blob changes value handling, and a polluted visitor can execute when an attacker already has the stronger ability to inject a function.

In Axios from version 1.7.0 to 1.20.0, the fetch adapter constructs a Request with sanitized resolvedOptions but then calls fetch with the original fetchOptions. A separate same-process prototype-pollution flaw populates Object.prototype.headers so fetchOptions.headers resolves through inheritance. The inherited fetchOptions.headers value overrides the sanitized Request headers through the second argument to fetch after Request construction. Attacker-controlled request headers can alter authorization, caching, metadata-service access, or application-specific behavior.