CVE-2026-59728 in astro
Summary
by MITRE • 07/28/2026
Astro is a web framework for content-driven websites. In versions 1.0.0 through 4.0.18, the source.title and enclosure.type item fields in packages/astro-rss/src/index.ts are interpolated directly into XML template strings without XML-character escaping before being parsed by fast-xml-parser. Both fields are validated only as z.string(), placing no restriction on XML special characters. An attacker who controls these values can inject arbitrary XML into the generated RSS feed: a value containing " can break out of an attribute (as with enclosure.type), and a value containing </source> can close an element early and inject additional nodes (as with source.title). This corrupts feed structure, injects false metadata (for example, a fake <link> pointing to a malicious URL), and can cause feed readers to misparse or display attacker-controlled content. In SSR mode (output: 'server'), the poisoned feed is served on every request to all subscribers. This issue has been fixed in version 4.0.19.
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Analysis
by VulDB Data Team • 07/28/2026
The vulnerability exists within the astro-rss package, a component of the Astro web framework used for building content-driven websites. This security flaw affects versions ranging from 1.0.0 through 4.0.18 and stems from improper input validation and sanitization in the RSS feed generation process. The issue specifically targets the source.title and enclosure.type fields within the packages/astro-rss/src/index.ts file where user-controllable data is directly interpolated into XML template strings without proper XML-character escaping mechanisms. Both fields are validated only as z.string() which provides no restrictions on XML special characters, creating a pathway for malicious input manipulation.
The technical execution of this vulnerability relies on XML parsing characteristics and injection patterns that exploit the lack of proper sanitization. When an attacker controls the source.title field containing a value with </source> tag, they can prematurely close the source element and inject additional XML nodes into the feed structure. Similarly, when the enclosure.type field contains a value with a quote character, it can break out of attribute boundaries and allow arbitrary XML injection. This represents a classic case of XML injection vulnerability where unescaped user input directly influences XML document structure. The vulnerability maps to CWE-91 and CWE-611 in the Common Weakness Enumeration catalog, specifically addressing improper neutralization of special elements used in XML and improper neutralization of data within XML.
The operational impact of this vulnerability is significant particularly in server-side rendering environments where the poisoned RSS feeds are served to all subscribers on every request. This creates a persistent attack vector that can affect multiple users simultaneously, potentially compromising feed readers that parse these maliciously constructed XML documents. The injected content can include false metadata such as malicious URLs in link elements, causing users to navigate to attacker-controlled websites. Feed readers may misparse the corrupted structure leading to display issues or potential execution of unintended code within vulnerable parsers. This vulnerability directly aligns with ATT&CK technique T1212 which describes exploitation of software vulnerabilities for data manipulation and injection attacks.
The security implications extend beyond simple content corruption as maliciously crafted RSS feeds can be used for phishing campaigns, drive-by download attacks, or information harvesting. In SSR mode where the feed is generated server-side on each request, any subscriber accessing the feed becomes a potential victim of this attack. The vulnerability affects the integrity of the RSS feed specification itself, potentially undermining trust in content delivery mechanisms and creating opportunities for more sophisticated attacks. Organizations using Astro framework with server-side rendering should immediately update to version 4.0.19 or later to mitigate this risk, as the fix addresses the root cause by implementing proper XML character escaping for user-controlled input fields before they are interpolated into XML templates.