PatchTheCVECVE-2026-120215: @fastify/cors is the CORS plugin for the Fastify web framework
CVE-2026-120215 is a low-severity flaw (CVSS 3.7) affecting affected software. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
@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
Why this priority
- Remotely exploitable, no login, no user action
No fix is published yet: follow the downgrade or mitigation steps.
Risk facts
| CVSS score | 3.7 (Low) |
| Attack vector | Network (remote) |
| Attack complexity | High |
| Privileges needed | None |
| User interaction | None |
| EPSS exploit chance | n/a |
| CISA exploited list | No |
| Weakness | CWE-248 |
| Published | 2026-11-02 |
| Last modified | 2026-11-02 |
Last updated 2026-11-02 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score
Timeline
- Published CVE record published
- Updated Record last modified
Advisories and coverage
Research and news
- VulDB Recent Entries: CVE-2026-120215 | fastify fastify-cors up to 11.3.x OnSend Hook reply.send onSend denial of service 2026-11-02
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.
Quick answers
How do I fix CVE-2026-120215?
No fixed release is listed yet. Watch the vendor advisory and apply any mitigation shown on this page.
Is CVE-2026-120215 being exploited?
CVE-2026-120215 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.
What does CVE-2026-120215 affect?
CVE-2026-120215 affects affected software. Severity is low (CVSS 3.7). @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 carri
How urgent is CVE-2026-120215?
Priority 18/100. Remotely exploitable, no login, no user action