# CVE-2026-126210: @hono/node-server: Backslash in the request path is parsed as a path separator, bypassing path-based access control at a reverse proxy

Status: published. Published: 2026-11-12. Updated: 2026-11-13.

@hono/node-server allows running the Hono application on Node.js. Prior to 1.19.18 and from 2.0.0 until 2.1.6, the server passes a raw request-target containing a backslash in its path to the WHATWG URL parser, which treats the backslash as a path separator and resolves dot segments. A reverse proxy, load balancer, or web application firewall that preserves the backslash and applies path-based rules to the original request can therefore permit a request that the application normalizes to a blocked route. This lets an unauthenticated client reach route content that the upstream component was intended to deny, while Hono application access controls are unaffected because they operate on the normalized path. This issue is fixed in versions 1.19.18 and 2.1.6.

## Remediation

- fix: @hono/node-server (npm): OSV reports a fixed version 2.1.6. Check the advisory for supported release branches. (source: OSV GHSA-jpvv-r467-5p4w) — https://github.com/advisories/GHSA-jpvv-r467-5p4w
- fix: @hono/node-server (npm): OSV reports a fixed version 1.19.18. Check the advisory for supported release branches. (source: OSV GHSA-jpvv-r467-5p4w) — https://github.com/advisories/GHSA-jpvv-r467-5p4w

## Affected products and versions

- honojs / node-server: >= 2.0.0, < 2.1.6 (affected); < 1.19.18 (affected). Source: CNA: GitHub_M
-  / @hono/node-server (@hono/node-server): ≥ 2.0.0; < 2.1.6 (affected, semver); OSV events: introduced 2.0.0; fixed 2.1.6. Source: OSV GHSA-jpvv-r467-5p4w
-  / @hono/node-server (@hono/node-server): ≥ 0; < 1.19.18 (affected, semver); OSV events: introduced 0; fixed 1.19.18. Source: OSV GHSA-jpvv-r467-5p4w

## Severity and prioritization

- CVSS 3.1: 5.3 (medium); CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N; source: CNA: GitHub_M

- CVSS 3.1: 5.3 (medium); CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N; source: NVD: security-advisories@github.com

- CISA KEV: No listing in collected sources

- EPSS: 0.38% as of 2026-11-13; percentile 31.95%

- SSVC: exploitation none; automatable yes; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-436

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/honojs/node-server/security/advisories/GHSA-jpvv-r467-5p4w (CNA: GitHub_M; x_refsource_CONFIRM)

- https://github.com/honojs/node-server/commit/3868998a805ae79216535ad3986c1e7228dee313 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/honojs/node-server/commit/fb97395ec36af66567c76976e741110b02804d1c (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/honojs/node-server/releases/tag/v1.19.18 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/honojs/node-server/releases/tag/v2.1.6 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/honojs/node-server/commit/3868998a805ae79216535ad3986c1e7228dee313 (security-advisories@github.com)

- https://github.com/honojs/node-server/commit/fb97395ec36af66567c76976e741110b02804d1c (security-advisories@github.com)

- https://github.com/honojs/node-server/releases/tag/v1.19.18 (security-advisories@github.com)

- https://github.com/honojs/node-server/releases/tag/v2.1.6 (security-advisories@github.com)

- https://github.com/honojs/node-server/security/advisories/GHSA-jpvv-r467-5p4w (security-advisories@github.com)

- https://github.com/advisories/GHSA-jpvv-r467-5p4w (OSV / GitHub Security Advisories; advisory)

- https://osv.dev/vulnerability/GHSA-jpvv-r467-5p4w (OSV / GitHub Security Advisories; osv)

## Provenance

- CNA: GitHub_M: https://www.cve.org/CVERecord?id=CVE-2026-126210; retrieved 2026-11-13; source updated 2026-11-13

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-126210; retrieved 2026-11-14; source updated 2026-11-13

- OSV / GitHub Security Advisories: https://osv.dev/vulnerability/GHSA-jpvv-r467-5p4w; retrieved 2026-11-12; source updated 2026-11-12

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-126210; retrieved 2026-11-13; source updated Not reported

Revision: be5e0ab8888b98722a4318ba946f8eef80f23f02363592a304cc3f16e70207e5

Canonical: https://y2.dev/cve/CVE-2026-126210

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