CVE-2026-13601: Yelp: yelp-xsl: overly permissive content security policy in yelp allows host file disclosure from flatpak applications
A flaw was found in Yelp due to an overly permissive Content Security Policy (CSP) implementation provided by yelp-xsl. A malicious Flatpak application can open crafted help content through the OpenURI portal. By embedding an untrusted CSS stylesheet within a structured SVG document, attacker-controlled content can bypass Flatpak's intended sandbox isolation, allowing Yelp to evaluate local XML inclusions and disclose arbitrary user-readable host files through remote CSS resource requests. This may result in the unauthorized disclosure of sensitive information.
Other sources
A local sandbox escape and host information disclosure flaw was found in Yelp. A regression introduced in the companion yelp-xsl stylesheet component targets the gnome-42 and master development branches, leaving the application's Content Security Policy (CSP) style handling directives overly permissive.
A malicious or compromised sandboxed Flatpak application can programmatically abuse the standard host org.freedesktop.portal.OpenURI portal interface to pass crafted help layout files (ghelp:// or mallard extensions). Because the system portal processes this request silently without requiring user interaction, host-level Yelp is automatically invoked to parse the file outside the application container. The attacker-controlled layout leverages local XML inclusions to load arbitrary host-level files into memory, which are subsequently exfiltrated out-of-band to a remote server using a background CSS url() query embedded inside a structured SVG document.
— Red Hat
Affected Software
Remediation
Event History
Frequently Asked Questions
What is the severity of CVE-2026-13601?
The severity of CVE-2026-13601 is rated as high with a score of 7.1.
How does CVE-2026-13601 impact system security?
CVE-2026-13601 allows a malicious Flatpak application to disclose host files by exploiting an overly permissive Content Security Policy in Yelp.
What software is affected by CVE-2026-13601?
The vulnerability affects the Yelp software and its yelp-xsl component.
How can I mitigate CVE-2026-13601?
Mitigation for CVE-2026-13601 involves updating Yelp to a version that addresses the overly permissive Content Security Policy issue.
What is the cause of CVE-2026-13601?
CVE-2026-13601 is caused by Yelp's implementation of an overly permissive Content Security Policy which allows untrusted CSS stylesheets in SVG documents.