CVE-2026-44488

Axios versions 1.7.0 through 1.15.x did not enforce configured request and response size limits when requests were sent with the fetch adapter. Applications that selected adapter: 'fetch', or ran in environments where axios resolved to the fetch adapter, could receive or send bodies larger than maxContentLength or maxBodyLength despite those limits being explicitly configured.

This can cause resource exhaustion in server-side usage when a malicious or compromised server returns an oversized response, when an attacker can supply a large data: URL, or when an application forwards attacker-controlled request bodies through axios while relying on maxBodyLength as a boundary.

Affected Functionality

Affected functionality includes requests using the built-in fetch adapter with finite maxContentLength or maxBodyLength values.

Relevant configurations include:

• adapter: 'fetch'
• adapter: ['fetch', ...] when fetch is selected
• environments where neither xhr nor http is available and axios falls back to fetch
• custom fetch environments configured through env.fetch

Unaffected functionality includes:

• Node.js default http adapter enforcement
• versions before the fetch adapter was introduced
• configurations that do not rely on finite axios size limits

Technical Details

In vulnerable versions, lib/adapters/fetch.js destructured request config without maxContentLength or maxBodyLength. The adapter dispatched fetch() and then materialized the response through text(), arrayBuffer(), blob(), or related resolvers without checking the configured response limit.

The fix in e5540dc added:

• maxContentLength and maxBodyLength reads in lib/adapters/fetch.js
• upfront data: URL decoded-size checks
• outbound body-size checks before dispatch
• Content-Length response pre-checks
• streaming response enforcement
• fallback checks for environments without ReadableStream
• regression tests in tests/unit/adapters/fetch.test.js

Proof of Concept of Attack

import http from 'node:http';
import axios from 'axios';

const server = http.createServer((req, res) => {
  let received = 0;

  req.on('data', chunk => {
    received += chunk.length;
  });

  req.on('end', () => {
    res.end(JSON.stringify({ received }));
  });
});

await new Promise(resolve => server.listen(0, resolve));
const url = `http://127.0.0.1:${server.address().port}/`;

await axios.post(url, 'A'.repeat(2 * 1024 * 1024), {
  adapter: 'fetch',
  maxBodyLength: 1024
});

// Vulnerable versions succeed and the server receives 2097152 bytes.
// Fixed versions reject with ERR_BAD_REQUEST.

server.close();

Workarounds

Use the Node.js http adapter for server-side requests where finite size limits are security-relevant.

Validate or cap attacker-controlled request bodies before passing them to axios.

Reject or strictly allowlist attacker-controlled URL schemes, especially data: URLs, before calling axios.

When Axios is used with adapter: 'fetch', configured body/response size limits are not enforced. This allows oversized uploads/downloads (including data: URLs) despite explicit limits, which can lead to memory/resource exhaustion in server-side usage.

Details

maxBodyLength and maxContentLength are not applied in the fetch adapter flow:

• lib/adapters/fetch.js (146-160): config destructuring does not include these controls.
• lib/adapters/fetch.js (220-234): request is dispatched with fetch() without request-size enforcement.
• lib/adapters/fetch.js (267-283): response is materialized via text(), arrayBuffer(), blob(), etc. without response-size checks.
  By contrast, the HTTP adapter enforces both limits.

PoC

Environment:

• Axios main at commit f7a4ee2
• Node v24.2.0

Steps:

1. Start an HTTP server that counts received bytes and echoes {received}.
2. Send 2 MiB with:
   • adapter: 'fetch'
   • maxBodyLength: 1024
3. Request a 4 KiB data: URL with:
   • adapter: 'fetch'
   • maxContentLength: 16

Expected secure behavior: both requests rejected.
Observed:

• Upload: success, server received 2097152
• data: response: success, length 4096

Impact

Type: DoS / resource exhaustion due to limit bypass.
Impacted: applications using Axios fetch adapter as a server-side security control boundary for untrusted request/response sizes.

The impact is availability-only. Affected applications may process, buffer, or transmit data beyond the configured limit, potentially exhausting memory, CPU, or network resources.

This does not affect axios’s default unlimited behaviour by itself: maxContentLength and maxBodyLength default to -1. The vulnerability exists when an application has configured finite limits and expects axios to enforce them.

Server-side runtimes are the primary concern. Browser impact is generally constrained by the browser process and browser fetch behavior, and should not be described as server process exhaustion.

The application allocates resources such as memory, threads, or file descriptors based on untrusted input without enforcing a cap. Typical impact: resource exhaustion leading to denial of service.

CVE-2026-44488 has a CVSS score of 7.5 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (1.16.0); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2026-44488? CVE-2026-44488 is a high-severity allocation of resources without limits or throttling vulnerability in axios (npm), affecting versions >= 1.7.0, < 1.16.0. It is fixed in 1.16.0. The application allocates resources such as memory, threads, or file descriptors based on untrusted input without enforcing a cap.
2. How severe is CVE-2026-44488? CVE-2026-44488 has a CVSS score of 7.5 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of axios are affected by CVE-2026-44488? axios (npm) versions >= 1.7.0, < 1.16.0 is affected.
4. Is there a fix for CVE-2026-44488? Yes. CVE-2026-44488 is fixed in 1.16.0. Upgrade to this version or later.
5. Is CVE-2026-44488 exploitable, and should I be worried? Whether CVE-2026-44488 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-44488 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-44488? Upgrade axios to 1.16.0 or later.