# CVE-2026-42455: LinkWarden: Stored XSS via Client-Side Archive Upload (Unsanitized HTML served from same origin)

> Attackers can execute arbitrary JavaScript in authenticated sessions by uploading unsanitized HTML archives, potentially leading to account takeover.

- **Severity:** High 8.8 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:H/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 8 May 2026
- **Updated:** 12 May 2026
- **Also known as:** GHSA-fjvg-mch3-j3vg

## What is CVE-2026-42455?

CVE-2026-42455 is a high-severity cross-site scripting vulnerability in linkwarden, published on 8 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Linkwarden is a self-hosted, open-source collaborative bookmark manager to collect, organize and archive webpages. In versions 2.14.0 and prior, the archive upload endpoint (POST /api/v1/archives/[linkId]?format=4) accepts HTML files (text/html) without sanitizing JavaScript content. When the archive is later accessed via GET /api/v1/archives/[linkId]?format=4, the HTML is served with Content-Type: text/html from the Linkwarden origin, without any Content-Security-Policy header. This allows arbitrary JavaScript execution in the context of the authenticated Linkwarden sessio. At time of publication, there are no publicly available patches.

Weakness: CWE-79 (Improper Neutralization of Input During Web Page Generation)

## Which versions are affected by CVE-2026-42455?


## How do I fix CVE-2026-42455?

No fix has been published for CVE-2026-42455 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-42455 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-42455 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-42455 and fix it if it is affected.

What it is: CVE-2026-42455 is a high-severity cross-site scripting vulnerability in linkwarden, published on 8 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-42455 exists.

Affected product: linkwarden. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-42455/ (Markdown: https://insights.sbomify.com/CVE-2026-42455/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-42455
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-42455
- OSV: https://osv.dev/vulnerability/CVE-2026-42455

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-42455/
Summaries are generated and may contain mistakes; the official description above is the record.