CVE-2026-47079 Round-trip Corruption via Improper Entity Escaping in xml_builder
Attackers can inject malicious scripts into XML output by exploiting improper entity escaping, leading to XSS in downstream consumers.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-47079?
CVE-2026-47079 is a low-severity cross-site scripting vulnerability in joshnuss xml_builder, published on 21 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
Inappropriate Encoding for Output Context vulnerability in joshnuss xml_builder (XmlBuilder module) allows Content Spoofing, Cross-site Scripting.
This vulnerability is associated with program files lib/xml_builder.ex and program routines XmlBuilder.generate/1, XmlBuilder.generate/2, XmlBuilder.escape_string/1, XmlBuilder.escape_entity/1.
XmlBuilder.generate/1 does not escape literal & characters in text or attribute values when they are followed by an entity-like token (lt;, gt;, amp;, quot;, apos;). As a result, attacker-supplied input such as <script> is emitted verbatim into the serialized XML rather than being escaped to &lt;script&gt;. When a downstream XML parser later reads the document, it decodes the entity sequences into the literal characters <script>, promoting inert-looking text into real markup. This allows an attacker to bypass upstream filters that block raw < and > characters, injecting markup into any downstream consumer that parses the produced XML and renders the text content in a markup-sensitive context (HTML, SVG, RSS/Atom feeds). Both element text and attribute values are affected.
This issue affects xml_builder: from 0.0.6 before 2.4.1.
Weakness: CWE-838
Which versions are affected by CVE-2026-47079?
1 open source package ship an affected version, including xml_builder.
| Package | Affected | Fixed in |
|---|---|---|
xml_builder Hex | From 0.0.6 | 2.4.1 |
How do I fix CVE-2026-47079?
Upgrade xml_builder to 2.4.1 or later.
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-2026-47079 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-47079 exists.
Sources
Also known as EEF-CVE-2026-47079, GHSA-5hjx-8g53-cmvm.