GNOME's help viewer, Yelp, last year was impacted by [1]a serious security issue for arbitrary file reads . There's a new vulnerability affecting the GNOME help viewer that led to the Yelp 49.1 release to address a possible Flatpak sandbox escape vector.

Thanks to funding provided by Germany's Sovereign Tech Agency with its Sovereign Tech Resilience program, Codean Labs was performing a security audit of Flatpak and various GNOME projects. In turn a significant Flatpak sandbox escape was discovered, related to last year's CVE.

GNOME developer Michael Catanzaro [2]explained of this issue that is now fixed in Yelp 49.1:

"In this case, a sandboxed application may launch Yelp to open a malicious help file. The help file can then exfiltrate arbitrary files from your host OS to a web server by using a CSS stylesheet embedded in an SVG. Suffice to say the attack is pretty clever, and certainly more impactful than the typical boring memory safety bugs I more commonly see."

The issue was originally [3]reported three months ago by Codean Labs due to Flatpak applications being able to exfilitrate host files over Yelp's Content Security Policy (CSP) being too permissive.

Yelp 49.1 is now [4]available with this fix.



[1] https://www.phoronix.com/news/GNOME-Yelp-Security-Issue-2025

[2] https://blogs.gnome.org/mcatanzaro/2026/05/11/flatpak-sandbox-escape-via-yelp/

[3] https://gitlab.gnome.org/GNOME/yelp/-/work_items/238

[4] https://gitlab.gnome.org/GNOME/yelp/-/commit/7856e7f79070f515282875212e1a90f09cfa5538