# CVE-2026-40472: Hackage package metadata stored XSS vulnerability

> Attackers can inject malicious scripts via package metadata, leading to stored XSS and potential account takeover on the Hackage server.

- **Severity:** Critical 9.9 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 23 Apr 2026
- **Updated:** 23 Apr 2026
- **Also known as:** GHSA-8fw8-47cx-j4q4, HSEC-2026-0004

## What is CVE-2026-40472?

CVE-2026-40472 is a critical cross-site scripting vulnerability in hackage-server, published on 23 Apr 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

In hackage-server, user-controlled metadata from .cabal files are rendered into HTML
href attributes without proper sanitization, enabling stored
Cross-Site Scripting (XSS) attacks.

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

## Which versions are affected by CVE-2026-40472?

1 open source package ship an affected version, including hackage-server.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `hackage-server` | Hackage | From 0.1 | None |

## How do I fix CVE-2026-40472?

No fix has been published for CVE-2026-40472 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-40472 being exploited?

There is no known exploitation of CVE-2026-40472 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-40472 and fix it if it is affected.

What it is: CVE-2026-40472 is a critical cross-site scripting vulnerability in hackage-server, published on 23 Apr 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-40472 in the wild and no public exploit code.

Affected packages and fixed versions:
- hackage-server (Hackage): affected from 0.1; no fix listed

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-2026-40472/ (Markdown: https://insights.sbomify.com/CVE-2026-40472/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-40472
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-40472
- OSV: https://osv.dev/vulnerability/CVE-2026-40472

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-40472/
Summaries are generated and may contain mistakes; the official description above is the record.