CVE-2026-120215: @fastify/cors · Uncaught Exception
Affects @fastify/corsSource CVE Database V5
Not known to be exploited · CVSS 3.7 Low : upgrade to 11.4.0 when convenient.
Data as of 2 Nov 2026, 11:12 UTC
Thin evidence
One scorer or none| CNA (openjs) | CVSS 3.1 | 3.7 |
|---|
- Patch
- Available – fixed in 11.4.0
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:LExploitation evidence
Disclosed: evidence found.
CVE published 2 Nov 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 2 Nov 2026.
What to do
Upgrade @fastify/cors to 11.4.0.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| @fastify/cors@fastify/cors | Affected
| Fixed in
|
npm@fastify/corspkg:npm/@fastify/corsOther threats | Affected
| Fixed in
|
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
Upgrade to @fastify/cors version 11.4.0 or later, where the onSend hook option is no longer accepted and registration fails with a clear error instead of crashing at runtime. As a workaround, avoid using the onSend hook by using other hooks such as the default onRequest, or set the preflight option to false to prevent the crash.
Description
@fastify/cors versions 8.2.0 through 11.3.x have a vulnerability where using the non-default onSend hook option causes the application to crash on CORS preflight OPTIONS requests. This happens because the plugin calls reply.send inside the onSend hook, triggering an uncaught ERR_HTTP_HEADERS_SENT error that can terminate the Node.js process. The issue is fixed in version 11.4.0, which disallows onSend as a hook option and fails registration with a clear error instead of crashing at runtime.