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.
- 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
- None listed
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 ", 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The earmark library is no longer maintained and has been retired on Hex.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
Which versions are affected by CVE-2026-48591?
3 open source packages ship an affected version, including earmark.
| Package | 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.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-48591 being exploited?
There is no known exploitation of CVE-2026-48591 in the wild and no public exploit code.
Sources
Also known as EEF-CVE-2026-48591, GHSA-52mm-h59v-f3c7.