# CVE-2026-128117: SvelteKit: Unhandled URIError when `reroute` rewrites a malformed pathname crashes adapter-node

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

SvelteKit is a framework for rapidly developing robust, performant web applications using Svelte. Prior to versions 2.70.4 and 3.1.1, the reroute hook could rewrite an invalid percent-encoded pathname into a valid route and reach a comparison that decoded the original malformed pathname outside the guarded decoding operation. The resulting unhandled URIError could crash an adapter-node server and deny service to other requests. This issue is fixed in 2.70.4 and 3.1.1.

## Remediation

- fix: @sveltejs/kit (npm): OSV reports a fixed version 3.1.1. Check the advisory for supported release branches. (source: OSV GHSA-mw6w-2fmv-pvw3) — https://github.com/advisories/GHSA-mw6w-2fmv-pvw3
- fix: @sveltejs/kit (npm): OSV reports a fixed version 2.70.4. Check the advisory for supported release branches. (source: OSV GHSA-mw6w-2fmv-pvw3) — https://github.com/advisories/GHSA-mw6w-2fmv-pvw3

## Affected products and versions

- sveltejs / kit: < 2.70.4 (affected); >= 3.0.0, < 3.1.1 (affected). Source: CNA: GitHub_M
-  / @sveltejs/kit (@sveltejs/kit): ≥ 3.0.0; < 3.1.1 (affected, semver); OSV events: introduced 3.0.0; fixed 3.1.1. Source: OSV GHSA-mw6w-2fmv-pvw3
-  / @sveltejs/kit (@sveltejs/kit): ≥ 0; < 2.70.4 (affected, semver); OSV events: introduced 0; fixed 2.70.4. Source: OSV GHSA-mw6w-2fmv-pvw3

## Severity and prioritization

- CVSS 3.1: 5.9 (medium); CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H; source: CNA: GitHub_M

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: exploitation none; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-248

## Exploit evidence

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

## References

- https://github.com/sveltejs/kit/security/advisories/GHSA-mw6w-2fmv-pvw3 (CNA: GitHub_M; x_refsource_CONFIRM)

- https://github.com/sveltejs/kit/pull/17620 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/sveltejs/kit/commit/0a2e58cbccdd46cac20aa5af4e2edf17e0da11dd (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/sveltejs/kit/commit/7993d5ebab017cb1be898a0b1c57371c5da06557 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/sveltejs/kit/releases/tag/@sveltejs/kit@2.70.4 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/sveltejs/kit/releases/tag/@sveltejs/kit@3.1.1 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/advisories/GHSA-mw6w-2fmv-pvw3 (OSV / GitHub Security Advisories; advisory)

- https://osv.dev/vulnerability/GHSA-mw6w-2fmv-pvw3 (OSV / GitHub Security Advisories; osv)

## Provenance

- CNA: GitHub_M: https://www.cve.org/CVERecord?id=CVE-2026-128117; retrieved 2026-11-13; source updated 2026-11-13

- OSV / GitHub Security Advisories: https://osv.dev/vulnerability/GHSA-mw6w-2fmv-pvw3; retrieved 2026-11-13; source updated 2026-11-13

Revision: 1641edb21c4e8b76338f771ff86e385f94f8342e1f6dc161c9bdcf9d66e1544d

Canonical: https://y2.dev/cve/CVE-2026-128117

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