CVE-2026-120215
@fastify/cors vulnerable to Denial of Service on a CORS preflight with the onSend hook
Description
@fastify/cors is the CORS plugin for the Fastify web framework. In versions 8.2.0 through 11.3.x, an application that registers the plugin with the non-default onSend hook option crashes on a CORS preflight. On an OPTIONS request that carries the Origin and Access-Control-Request-Method headers, the plugin calls reply.send from inside the onSend hook and re-enters the send pipeline, so a second write of the response headers throws an uncaught ERR_HTTP_HEADERS_SENT that can terminate the Node.js process when no process-level handler is installed. An unauthenticated remote client can trigger this with a single preflight request, so the impact is availability only, and exploitation requires the non-default onSend configuration. The issue is fixed in @fastify/cors 11.4.0, where onSend is no longer an accepted hook value and registration fails with a clear error instead of crashing at request time, and users should upgrade to 11.4.0 or later. As a workaround, use any other hook such as the default onRequest, or set preflight to false.
INFO
Published Date :
Nov. 2, 2026, 11:17 a.m.
Last Modified :
Nov. 2, 2026, 5:17 p.m.
Remotely Exploit :
No
Source :
ce714d77-add3-4f53-aff5-83d477b104bb
Affected Products
The following products are affected by CVE-2026-120215
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
No affected product recoded yet
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 3.1 | LOW | ce714d77-add3-4f53-aff5-83d477b104bb |
Solution
- Upgrade @fastify/cors to version 11.4.0 or later.
- Alternatively, use a different hook like onRequest.
- Alternatively, set preflight to false in the plugin configuration.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-120215.
| URL | Resource |
|---|---|
| https://cna.openjsf.org/security-advisories.html | |
| https://github.com/fastify/fastify-cors/security/advisories/GHSA-8c3j-mm64-257c |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-120215 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-120215
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-120215 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-120215 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Nov. 02, 2026
Action Type Old Value New Value Added SSVC {'id': 'CVE-2026-120215', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'none'}, {'automatable': 'no'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-11-02T17:03:55.457723Z'} -
New CVE Received by ce714d77-add3-4f53-aff5-83d477b104bb
Nov. 02, 2026
Action Type Old Value New Value Added Description @fastify/cors is the CORS plugin for the Fastify web framework. In versions 8.2.0 through 11.3.x, an application that registers the plugin with the non-default onSend hook option crashes on a CORS preflight. On an OPTIONS request that carries the Origin and Access-Control-Request-Method headers, the plugin calls reply.send from inside the onSend hook and re-enters the send pipeline, so a second write of the response headers throws an uncaught ERR_HTTP_HEADERS_SENT that can terminate the Node.js process when no process-level handler is installed. An unauthenticated remote client can trigger this with a single preflight request, so the impact is availability only, and exploitation requires the non-default onSend configuration. The issue is fixed in @fastify/cors 11.4.0, where onSend is no longer an accepted hook value and registration fails with a clear error instead of crashing at request time, and users should upgrade to 11.4.0 or later. As a workaround, use any other hook such as the default onRequest, or set preflight to false. Added CVSS V3.1 AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L Added CWE CWE-248 Added Affected New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/120xxx/CVE-2026-120215.json">CVE-2026-120215</a> Added Reference https://cna.openjsf.org/security-advisories.html Added Reference https://github.com/fastify/fastify-cors/security/advisories/GHSA-8c3j-mm64-257c