Log in Start free

Vulnerability · Published Jul 27, 2026 · Assigned by GitHub_M

CVE-2026-59728@astrojs/rss: XML Injection via Unescaped RSS Feed Fields

Medium 4.3

In plain English

A medium-severity security flaw in astro from withastro. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 25% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)4.3Medium
Exploit odds (30 days)0.3%top 74.6% of all CVEs
Exploited in the wildNo reportsCISA SSVC: poc
Attack toolingNoneno public tooling known

Official description

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.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
npm@astrojs/rss4.0.19GHSA-8j5q-mfj2-5q9q

Affected products (as reported)

VendorProductVersions
withastro astro >= 1.0.0, < 4.0.19

Weakness: CWE-91 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N

References