# CVE-2026-48591: Stored XSS via unescaped HTML attribute values in earmark

> Stored XSS in earmark allows attackers to execute arbitrary JavaScript via unescaped HTML attributes in Markdown links.

- **Severity:** Medium 4.8 (`CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 17 Jun 2026
- **Updated:** 18 Jun 2026
- **Also known as:** EEF-CVE-2026-48591, GHSA-52mm-h59v-f3c7

## What is CVE-2026-48591?

CVE-2026-48591 is a medium-severity cross-site scripting vulnerability in pragdave earmark, published on 17 Jun 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

### Official description

Improper Neutralization of Script in Attributes in a Web Page vulnerability in pragdave earmark allows stored cross-site scripting via unescaped HTML attribute values.

'Elixir.Earmark.Transform':_make_att1/2 in lib/earmark/transform.ex splices attribute values verbatim between two literal " bytes: [" ", name, "=\"", value, "\""]. Text nodes are routed through the existing escape function which encodes " as &quot;, but attribute values never visit that path. A markdown link whose URL or title contains a bare " closes the attribute early and lets the trailing bytes be parsed by the browser as fresh HTML attributes. For example, [click](http://example.com/?a=x" onerror="alert(1)) renders as <a href="http://example.com/?a=x" onerror="alert(1)">click</a>, executing arbitrary JavaScript in the victim's browser.

The earmark library is no longer maintained and has been retired on Hex. No patched version will be released. All releases from 1.4.1 onward are affected, and users should migrate to a maintained Markdown library such as MDEx.

This issue affects earmark from 1.4.1 onward.

Weakness: CWE-83 (Improper Neutralization of Script in Attributes in a Web Page)

## Which versions are affected by CVE-2026-48591?

3 open source packages ship an affected version, including earmark.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `earmark` | Hex | From 1.4.1 | None |
| `earmark` | Hex | From 1.4.1 to 1.5.0-pre1 | None |
| `earmark` | Hex | From 1.4.1 to 1.5.0-pre1 | None |

## How do I fix CVE-2026-48591?

No fix has been published for CVE-2026-48591 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-48591 being exploited?

There is no known exploitation of CVE-2026-48591 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-48591 and fix it if it is affected.

What it is: CVE-2026-48591 is a medium-severity cross-site scripting vulnerability in pragdave earmark, published on 17 Jun 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-48591 in the wild and no public exploit code.

Affected packages and fixed versions:
- earmark (Hex): affected from 1.4.1; no fix listed
- earmark (Hex): affected from 1.4.1 up to 1.5.0-pre1; no fix listed
- earmark (Hex): affected from 1.4.1 up to 1.5.0-pre1; 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-2026-48591/ (Markdown: https://insights.sbomify.com/CVE-2026-48591/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-48591
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-48591
- OSV: https://osv.dev/vulnerability/CVE-2026-48591

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-48591/
Summaries are generated and may contain mistakes; the official description above is the record.