CVE-2026-120216
fastify vulnerable to Denial of Service via uncaught exception on handlerTimeout with streaming responses
No exploitation reported by the sources we read.
- Published2026-11-02
- WeaknessCWE-248
Am I affected?
Debian, Ubuntu or Red Hat sometimes backport a fix without changing the upstream version number: such a version reads « to verify », never « affected ».With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.
Description
fastify is a web framework for Node.js. In versions 5.8.0 through 5.12.7, when the server is configured with a nonzero handlerTimeout and a route returns a streaming response, a request whose stream has already sent its headers but stays open past the timeout crashes the server. When the timeout fires, Fastify tries to send a new error response on a response that has already started, raising an uncaught ERR_HTTP_HEADERS_SENT that terminates the Node.js process and interrupts any other in-flight requests. An unauthenticated remote client can trigger this with a single request to an affected streaming endpoint, so the impact is availability only, and exploitation requires the non-default handlerTimeout to be set. The default handlerTimeout of 0 is not affected. The issue is fixed in fastify 5.12.8, and users should upgrade to 5.12.8 or later. As a workaround, set handlerTimeout to 0, which disables the affected timeout path.
Timeline
dates in UTC- 2026-11-0211:08CVE publishedCNA
Observed activity
isMalicious corpus · updated 2026-11-02 09:37 UTCBlock these indicators
- Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2026-120216?format=txt
- CSV export: https://api.ismalicious.com/edl/cve/CVE-2026-120216?format=csv
- TAXII collection of exploited CVEs
- The EDL and CSV take an API key on the Pro plan.
Versions per branch
Products declared by the CNA
As openjs, the CNA that assigned this CVE, declared them in the CVE record; versions as written. NVD lists no product for this CVE yet: this is the only product data so far.
- fastifyother versions: not affectedAffected
- ≥ 5.8.0, < 5.12.8fixed in 5.12.8semver
Not affected = 5.12.8
Source: the CNA record (CVE Program), © The MITRE Corporation,CVE Terms of UseCVE recordupdated 2026-11-02
Neither OSV.dev nor the vendor advisories we read list affected versions for CVE-2026-120216 yet.
Fix
No fix published by the sources we read yet. NVD record
Detection
- Nuclei template
- none so far ProjectDiscovery
- Exploit-DB
- no entry Exploit-DB
- Proof-of-concept repositories
- none listed PoC-in-GitHub
- Metasploit modules
- none listed Metasploit Framework
Sources
Identifiers
- EUVD-2026-115128same flawENISA EUVD · LicenseRef-ENISA-legal-notice
Technical details
- CVSS v3 Vector
- CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
- Published
- 2026-11-02
- Last Modified
- 2026-11-02
- NVD status
- Received
Frequently asked questions
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