CVE-2026-13601 describes a security flaw in Yelp's yelp-xsl component where an overly permissive Content Security Policy enables a malicious Flatpak application to exploit the OpenURI portal. By embedding an untrusted CSS stylesheet inside a structured SVG document, the attacker can bypass Flatpak sandbox isolation. This allows Yelp to process local XML inclusions and disclose arbitrary user-readable files on the host system via remote CSS resource requests. The vulnerability has a CVSS 3.1 score of 7.1 (High) with vector AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N, indicating local attack vector, low complexity, no privileges or user interaction required, with a scope change and high confidentiality impact but no integrity or availability impact. Red Hat has released patches for affected versions of Yelp on Red Hat Enterprise Linux 8 and 9 to fix this issue.

Successful exploitation of this vulnerability allows a local attacker with the ability to run a malicious Flatpak application to bypass sandbox restrictions and cause Yelp to disclose arbitrary user-readable files from the host system. This leads to unauthorized disclosure of sensitive information, impacting confidentiality. There is no impact on integrity or availability. The vulnerability requires local access and does not require user interaction or privileges, but it does involve a scope change due to sandbox bypass.

Red Hat has released official security updates for Yelp on Red Hat Enterprise Linux 8 and 9 that address this vulnerability. Users and administrators should apply these updates promptly to remediate the issue. For detailed update instructions, refer to the Red Hat advisory and article at https://access.redhat.com/articles/11258. No additional mitigations are indicated by the vendor advisory.