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CVE-2026-92081 medium CVSS 5.9

Vulnerability in fastify (CVE-2026-92081)

Summary

Vulnerability in fastify (CVE-2026-92081). Risk of unauthorized operations or information disclosure. Exploitable via fastify. Mitigation: upgrade to 5.12.5 or later.

Original description

The description as published by the source.

Impact

fastify crashes with an uncaught ERR_HTTP2_INVALID_CONNECTION_HEADERS exception when a route that registers a response trailer via reply.trailer() is served over HTTP/2. Fastify unconditionally adds the Transfer-Encoding: chunked header when a trailer is set, which is forbidden on HTTP/2, so Node.js throws while serializing the response headers. The exception is not caught and becomes an uncaughtException, terminating the Node.js process.

One unauthenticated HTTP/2 request to any route that uses trailers is enough to crash the server, dropping all in-flight requests, and the request can be repeated to keep the process down. Applications are affected only when HTTP/2 is enabled (http2: true) and at least one route registers a trailer. HTTP/1.x responses are not affected.

Patches

Upgrade to fastify 5.12.5 or later.

Workarounds

Avoid registering response trailers with reply.trailer() on routes served over HTTP/2 until upgrading.

Source: NIST National Vulnerability Database NVD GitHub Advisory

Auto-generated summary

Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.

A vulnerability tracked as CVE-2026-92081 has been found in fastify.
Attackers can target a specific entry point like fastify over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 5.9/10.
What to do: upgrade fastify to 5.12.5 or later.
If unsure, ask your IT team or search "fastify CVE-2026-92081" on the vendor's site.

CVE-2026-92081 (fastify) — CWE-248 / CVSS v3 5.9
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: fastify / ERR_HTTP2_INVALID_CONNECTION_HEADERS
Patched: 5.12.5 — apply immediately
Workaround: Avoid registering response trailers with reply.trailer() on routes served over HTTP/2 until upgrading.
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.

❓ What is the problem

A vulnerability (CWE-248) exists in fastify. Attackers reach the vulnerable code path via fastify without authentication.

📍 Affected scope

Check the vendor advisory for the affected versions of fastify. Attack surface: fastify / ERR_HTTP2_INVALID_CONNECTION_HEADERS.

🔥 Severity

Severity: Medium (CVSS 5.9/10). Risk of unauthorized operations or information disclosure.

🔧 How to fix

Update to 5.12.5.

🛡️ Workaround

Workaround: Avoid registering response trailers with reply.trailer() on routes served over HTTP/2 until upgrading.

🔍 Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'fastify' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

  1. 1
    Identify exposure identify 
    grep -r 'fastify' . | grep -v node_modules

    リポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で fastify を grep し、稼働しているサービス・バージョンを把握する。

  2. 2
    Apply temporary workaround mitigate 
    Avoid registering response trailers with `reply.trailer()` on routes served over HTTP/2 until upgrading.

    パッチが適用されるまでの応急処置として、Avoid registering response trailers with reply.trailer() on routes served over HTTP/2 until upgrading. を実施。回避策の副作用 (機能低下) を確認した上で。

  3. 3
    Apply patch patch 
    Upgrade fastify to 5.12.5

    ステージング環境で 5.12.5 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。

  4. 4
    Post-deployment verification verify 
    Confirm patched version is live in production

    パッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。

Affected packages

npm fastify
[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"5.12.5"}]}]

References

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