# CVE-2026-59728

## Summary

- **CVE ID:** CVE-2026-59728
- **Severity:** MEDIUM
- **CVSS Score:** 4.3 (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N)
- **CWE:** CWE-91
- **Published:** Jul 27, 2026
- **Last Modified:** Jul 28, 2026

## 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 Products

- withastro — astro (>= 1.0.0, < 4.0.19)

## References

- [CNA](https://github.com/withastro/astro/security/advisories/GHSA-8j5q-mfj2-5q9q)
- [CNA](https://github.com/withastro/astro/pull/17209)
- [CNA](https://github.com/withastro/astro/commit/fbcfa039dfe3d700b239f595a6c55ee35e45bd06)
- [CNA](https://github.com/withastro/astro/releases/tag/@astrojs/rss@4.0.19)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.27%
- **EPSS Percentile:** 18.4

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-11._