Affects me too: - Kubuntu 26.04 LTS - fontconfig 2.17.1 - fonts-katex and libjs-katex 0.16.10+~cs6.1.0-5ubuntu1 - (lemonade-server not installed) - Google Chrome 154.0.8037.57 (.deb).
(full disclosure: I tried debugging this using Claude Code, and Claude code helped me write this message, which I have fully reviewed before posting) Same trace (FcCharSetHasChar <- QFontEngineMultiFontConfig::shouldLoadFontEngineForCharacter <- ... <- Klipper), kioworker crashing too, and ``fc-match sans`` returned `KaTeX_AMS-Regular.woff`. The workaround in the description fixed it. Some observations that may help narrow this down. I have not found the root cause. 1. The broken `~/.cache/fontconfig` held, for each directory, a real `*-le64.cache-12` file plus symlinks `*-le64.cache-9`, -10 and -11 pointing to it. The system library only uses format 9 (`grep -ao "\.cache-[0-9]*" /usr/lib/x86_64-linux-gnu/libfontconfig.so.1` gives only .cache-9), and a cache it builds has plain cache-9 files with no symlinks. 2. On my machine, Google Chrome (which appears to bundle a newer fontconfig) writes these. With a clean cache and Chrome closed, launching Chrome created 33 cache-12 files. With XDG_CACHE_HOME pointed at a temporary directory, Chrome wrote cache-12 files there plus the cache-9/10/11 symlinks. This matches the compat workaround the fontconfig maintainer describes in https://github.com/flatpak/flatpak/issues/6738. 3. Timeline, similar to the description's note that clearing only the user cache fixed it for a single login: after a clean rebuild, a login worked with fonts-katex still installed. After I used Chrome, the user cache was refilled with cache-12 files and symlinks, and the next boot crash-looped again. 4. Isolated test, with fonts-katex NOT installed: I copied the 40 KaTeX .woff/.woff2 files from the package into ~/.local/share/fonts/katex-test. - The system fontconfig 2.17.1 cached them correctly (`fc-cat` shows e.g. "KaTeX_AMS-Regular.woff" 0 "KaTeX_AMS:familylang=en:style=Regular:..."), and `fc-match sans` stayed NotoSans-Regular.ttf. So in this location, I could not reproduce the malformed cache generation described in comment #3. - I ran Chrome with XDG_CACHE_HOME pointed at a temporary directory. The system `fc-cat` could not load Chrome's cache-12 file for the KaTeX directory ("Unable to load the cache"), while it read Chrome's cache-12 files for TTF directories fine. - However, `XDG_CACHE_HOME=<Chrome's cache dir> fc-match -v sans` still returned NotoSans-Regular.ttf with a normal family, style and fontversion. So Chrome's cache alone did not reproduce the poisoning in this setup. Not tested: the fonts in their real location (/usr/share/fonts/truetype/katex), where the root-owned cache in /var/cache/fontconfig is also involved. Comment #3 found the problem only appears when the user cache is used, so the interaction between the system and user caches may matter. For others hitting this: do you have *.cache-12 files and symlinks in ~/.cache/fontconfig? Chrome 154 stable started rolling out on 2026-09-22, close to the breakage dates reported here; that may be a coincidence. Related: https://bugs.kde.org/show_bug.cgi?id=525636, https://github.com/flatpak/flatpak/issues/6738, https://github.com/lemonade-sdk/lemonade/issues/3655 ** Bug watch added: github.com/flatpak/flatpak/issues #6738 https://github.com/flatpak/flatpak/issues/6738 ** Bug watch added: KDE Bug Tracking System #525636 https://bugs.kde.org/show_bug.cgi?id=525636 ** Bug watch added: github.com/lemonade-sdk/lemonade/issues #3655 https://github.com/lemonade-sdk/lemonade/issues/3655 -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/2168311 Title: Default-installed fonts-katex crashes fontconfig (FcCharSetHasChar); Plasma won't start To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/node-katex/+bug/2168311/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
