CVE-2026-92081
CVE-2026-92081 — fastify vulnerable to Denial of Service via unhandled exception on HTTP/2 trailer responses
fastify is a fast and low-overhead web framework for Node.js. In versions before 5.12.5, when a route registers a response trailer via reply.trailer() and is served over HTTP/2, fastify unconditionally sets the Transfer-Encoding: chunked header, which is forbidden on HTTP/2, so Node.js throws while serializing the response headers. The exception is not caught and becomes an uncaughtException, so a single unauthenticated HTTP/2 request to any route that uses trailers crashes the server process and drops all in-flight requests, and it can be repeated on every restart. The issue is fixed in fastify 5.12.5, and users should upgrade to 5.12.5 or later. As a workaround, avoid registering response trailers with reply.trailer() on routes served over HTTP/2 until upgrading.
Published Updated Sources: NVD, fastify (CNA), GitHub, Red Hat (VEX), SOCRadar CTI
Triage
Is it exploited, how likely is exploitation, what does it touch, and how severe do the scoring sources call it.
Exploitation
Exploit code
public exploit, none observed
EPSS
0%
ahead of 0% of scored CVEs
CVSS base
5.9
medium
Remediation
The vendor's own words where we have them.
Upgrade fastify to a fixed release (5.12.5). Apply vendor patches per advisory and restrict external exposure of the affected component until patched.
Red Hat VEX · CVE-2026-92081
none_available: Fix deferred
First 24 hours
Ordered from the record's own fields — exposure first, because you cannot patch what you have not found.
- Identify exposed assets running affected vendor/product/version combinations.
- Prioritize based on EPSS, PoC availability, and external exposure.
- Search available logs for exploit probes, errors, authentication anomalies, or suspicious child processes matching the vulnerability class.
Affected scope
Vendor, product and version as the advisories word them.
| Vendor | Product | Versions | Status |
|---|---|---|---|
| fastify | fastify | 0 to < 5.12.5 | Vulnerable |
| fastify | fastify | 5.12.5 | Patched |
Attack characteristics
The CVSS vector, decoded. It describes the attack, not your exposure to it.
Availability
High
Confidentiality
None
Integrity
None
Scope
Unchanged
Attack Complexity
High
Attack Vector
Network
Privileges Req
None
User Interaction
None
Every base score collected
Sources score independently and disagree; each row says who scored it and under which version.
| Score | Version | Severity | Expl. | Impact | Source |
|---|---|---|---|---|---|
| 5.9 | CVSS 3.1 | medium | 2.2 | 3.6 | CNA, fastify (CNA), Red Hat (VEX) |
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
What this weakness leads to
MITRE's own consequences and mitigations for the weakness class — the authority's wording, not guidance derived from the CVSS vector.
CWE-248 · Uncaught Exception
- DoS: Crash, Exit, or Restart
- Read Application Data
Weakness & attack patterns
- CWE-248
Inferred from the weakness class — not observed against this CVE.
Public exploit
Capability, not use: code existing is a different claim from anyone running it.
Repositories
1
Detection
Read off the CVSS vector and the weakness class. Starting points, not rules we have tested.
- Search application, proxy, and WAF logs for requests touching /2.
- Prioritize edge telemetry for network-reachable fastify.
- Monitor for scanner or exploit-pattern traffic after 1 public PoC repositories were reported.
Timeline
What happened to this CVE, newest first — with the readings a source repeats on a schedule counted underneath rather than listed.
- 2026
Added · CVSS 3.1 5.9 (AV:N)
Sep 16, 2026 · NVD
Initial · CVE published
Sep 16, 2026 · NVD
CVE published by MITRE.
Sep 16, 2026 · SOCRadar CTI
References
6 on the record
- cna.openjsf.org/security-advisories.html
Vendor Advisory
- github.com/fastify/fastify/security/advisories/GHSA-4mh8-r7rc-xpvc
Exploit, Third Party Advisory
- access.redhat.com/security/cve/CVE-2026-92081
Vendor Advisory
- bugzilla.redhat.com/show_bug.cgi?id=2535071
Vendor Advisory
- www.cve.org/CVERecord?id=CVE-2026-92081
Vendor Advisory
- nvd.nist.gov/vuln/detail/CVE-2026-92081
NVD
Elsewhere on this site
- fastifyevery CVE for this vendor
- Denial of Servicesame class
- CWE-248other pages naming this weakness
Not in any source we poll
Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.
- No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
- No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
- No exploit packet captures, log samples, or incident case IDs supplied.
Answered from this record1
What should defenders know first?
CVE-2026-92081 is fastify vulnerable to Denial of Service via unhandled exception on HTTP/2 trailer responses, a medium vulnerability affecting fastify from fastify. The current evidence does not list it in CISA KEV, and the exploit status is: Active exploitation is not confirmed from current sources for CVE-2026-92081. Public exploit evidence is: 1 public PoC repositories reported; 0 marked weaponized in current dataset. The affected-version evidence is listed in the key facts and affected products tables. Defenders should first verify whether exposed or business-critical assets run those versions, then apply vendor patches or mitigations, restrict reachable attack surface, and preserve logs for detection review. CVSS 5.9 describes technical severity, while EPSS 0% helps estimate near-term exploit likelihood; neither replaces asset context. Unknown fields should remain explicit in tickets, and threat actor, IOC, victimology, or payload claims should not be added unless a cited source supports them. Monitor CISA KEV, vendor advisories, NVD changes, public PoC repositories, and internal telemetry for update triggers.