EEF-CVE-2026-48591 CVE-2026-48591 GHSA-52mm-h59v-f3c7
Stored XSS via unescaped HTML attribute values in earmark
- Severity
- 0.0 / 10
- Medium · CVSS 4.0
- Exploit chance (EPSS)
- 0.13%
- Chance of exploitation in the next 30 days. Higher than 2.85% of scored vulnerabilities.
- Known exploited
- No
- Not in CISA's catalog
- Weakness
- CWE-83 Improper Neutralization of Script in Attributes in a Web Page
- Fix
- None yet
- No fixed version published
Description
Summary
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The earmark library is no longer maintained and has been retired on Hex.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.
Workarounds
Migrate to a maintained Markdown library such as MDEx (https://hex.pm/packages/mdex). The earmark package has been retired on Hex and no patched release will be made.
Affected versions
Hex
How to fix
No fixed version has been published yet. Until one is, remove or replace the package, or turn off or isolate the affected feature. This page updates when a fix ships.
Severity breakdown
CVSS 4.0 0.0
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
- Attack vector
- Local
- Attack complexity
- Low
- Attack requirements
- None
- Privileges required
- None
- User interaction
- Passive
- Confidentiality (vulnerable system)
- Low
- Integrity (vulnerable system)
- Low
- Availability (vulnerable system)
- None
- Confidentiality (subsequent systems)
- Low
- Integrity (subsequent systems)
- Low
- Availability (subsequent systems)
- None
Weakness
CWE-83: Improper Neutralization of Script in Attributes in a Web Page
The product does not neutralize or incorrectly neutralizes "javascript:" or other URIs from dangerous attributes within tags, such as onmouseover, onload, onerror, or style.
How to prevent it
- Implementation: Carefully check each input parameter against a rigorous positive specification (allowlist) defining the specific characters and format allowed. All input should be neutralized, not just parameters that the user is supposed to specify, but all data in the request, including tag attributes, hidden fields, cookies, headers, the URL itself, and so forth. A common mistake that leads to continuing XSS vulnerabilities is to validate only fields that are expected to be redisplayed by the site. We often encounter data from the request that is reflected by the application server or the application that the development team did not anticipate. Also, a field that is not currently reflected may be used by a future developer. Therefore, validating ALL parts of the HTTP request is recommended.
- Implementation: Use and specify an output encoding that can be handled by the downstream component that is reading the output. Common encodings include ISO-8859-1, UTF-7, and UTF-8. When an encoding is not specified, a downstream component may choose a different encoding, either by assuming a default encoding or automatically inferring which encoding is being used, which can be erroneous. When the encodings are inconsistent, the downstream component might treat some character or byte sequences as special, even if they are not special in the original encoding. Attackers might then be able to exploit this discrepancy and conduct injection attacks; they even might be able to bypass protection mechanisms that assume the original encoding is also being used by the downstream component. The problem of inconsistent output encodings often arises in web pages. If an encoding is not specified in an HTTP header, web browsers often guess about which encoding is being used. This can open up the browser to subtle XSS attacks.
- Implementation: With Struts, write all data from form beans with the bean's filter attribute set to true.
- Implementation: To help mitigate XSS attacks against the user's session cookie, set the session cookie to be HttpOnly. In browsers that support the HttpOnly feature (such as more recent versions of Internet Explorer and Firefox), this attribute can prevent the user's session cookie from being accessible to malicious client-side scripts that use document.cookie. This is not a complete solution, since HttpOnly is not supported by all browsers. More importantly, XmlHttpRequest and other powerful browser technologies provide read access to HTTP headers, including the Set-Cookie header in which the HttpOnly flag is set.
References
Advisories
Packages
Other links
Timeline
- Published
- Last updated by the source
- Latest EPSS score
Related advisories
| Advisory | Severity | Why it's related |
|---|---|---|
| GHSA-7pw4-f3q4-r2p2 Astro: Cross-site scripting via unescaped transition:* directive values on hydrated islands | Low | Same weakness, CWE-83 |
| GHSA-rhj6-r49h-5932 Kirby: Self cross-site scripting (self-XSS) in the writer field | High | Same weakness, CWE-83 |
| GHSA-w9hf-3pp7-pvxv OpenClaw: Exported session HTML could keep unsafe markdown links | Low | Same weakness, CWE-83 |
| GHSA-934w-87qh-qr26 Nuxt: Reflected XSS in `<NuxtLink>` via unsanitised `javascript:` or `data:` URL | Medium | Same weakness, CWE-83 |
| GHSA-f73j-pm2c-rxvr Concrete CMS is Vulnerable to Reflected XSS in Legacy Pagination | Medium | Same weakness, CWE-83 |
| GHSA-fx6j-w5w5-h468 Nuxt: Reflected XSS in `navigateTo()` external redirect | Medium | Same weakness, CWE-83 |
| GHSA-vf6r-87q4-2vjf nuxt vulnerable to Cross-site Scripting in navigateTo if used after SSR | Medium | Same weakness, CWE-83 |
Credits: Jonatan Männchen / EEF, Peter Ullrich, Robert Dober
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