CVE-2026-120216: fastify · Uncaught Exception
Affects fastifySource CVE Database V5
Not known to be exploited · CVSS 5.9 Medium : upgrade to 5.12.8 when convenient.
Data as of 2 Nov 2026, 11:43 UTC
Thin evidence
One scorer or none| CNA (openjs) | CVSS 3.1 | 5.9 |
|---|
- Patch
- Available – fixed in 5.12.8
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:HExploitation 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 to 5.12.8.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| fastifyfastify | Affected
| Fixed in
|
npmfastifypkg:npm/fastifyOther 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 fastify to version 5.12.8 or later, where this issue is fixed. As a temporary workaround, set handlerTimeout to 0 to disable the affected timeout path.
Description
A vulnerability in fastify versions 5.8.0 through 5.12.7 causes the server to crash when a streaming response exceeds a configured nonzero handlerTimeout. This occurs because Fastify attempts to send an error response after headers have already been sent, triggering an uncaught exception that terminates the Node.js process and disrupts other requests. The issue affects availability and can be triggered remotely without authentication. The default handlerTimeout of 0 is not affected. The vulnerability is fixed in version 5.12.8.