CVE-2026-13601

This vulnerability affects the Content Security Policy (CSP) implementation handling help documents rendered outside the application container via the Flatpak OpenURI portal. Red Hat Product Security has rated this issue as Important.

The flaw is caused by an overly permissive Content Security Policy (CSP) implementation that allows attacker-controlled help content to bypass Flatpak's intended sandbox isolation. A malicious Flatpak application can invoke Yelp through the standard OpenURI portal and supply crafted help content that causes the application to access and disclose arbitrary user-readable files from the host system.

Unlike typical local file disclosure vulnerabilities, exploitation does not require privileges on the vulnerable Yelp application itself. A malicious Flatpak application can invoke Yelp through the standard OpenURI portal without requiring additional authorization or user interaction beyond running the application. Because the vulnerability enables a sandboxed Flatpak application to access resources outside its intended security boundary by leveraging the host's Yelp application, Red Hat Product Security considers this a cross-boundary information disclosure vulnerability. Under these conditions, an attacker may disclose arbitrary user-readable files from the host system. The currently available analysis does not demonstrate impacts to integrity or availability.

This flaw arises as an upstream regression that reintroduced part of the functionality previously addressed by CVE-2025-3155.

The original upstream remediation for CVE-2025-3155 required coordinated changes in both the yelp application and the yelp-xsl stylesheet package. Red Hat Enterprise Linux streams that previously received backported fixes for CVE-2025-3155 are also affected by this regression.

For CVE-2026-13601, upstream has chosen to remediate the remaining vulnerability entirely within the yelp application. Consequently, this issue is remediated exclusively through security updates to the yelp package, and no additional updates to yelp-xsl are required for this CVE. Systems are fully protected once the corresponding yelp security update has been applied.

Hence, Red Hat Enterprise Linux is only required to update "yelp" package to get the fix.

Although RHEL 10 and RHIVOS ship versions of yelp-xsl, the yelp application is not shipped or supported on those platforms. As a result, the vulnerable execution path is not present and those products are not affected.