Affects me too, third machine, Kubuntu 26.04.1 LTS, stock install. fonts-katex 0.16.10+~cs6.1.0-5ubuntu1 (in the installer package set), libfontconfig1 2.17.1-3ubuntu1, Plasma 6.6.6, Qt 6.10.2, kernel 7.0.0-34, Wayland.
And yes, i took help with AI to identify my own problem and the matching regarding this ticket. Broke on 2026-09-24 after apt upgrade (Plasma 6.6.4->6.6.6, fonts-opensymbol). fontconfig trigger ran 10:03:50; plasmashell crash loop 10:15:53-10:16:01 (4 coredumps: SIGABRT "malloc(): unaligned tcache chunk detected" in KSvg::Svg::image, then repeated SIGSEGV). Same backtrace: FcCharSetHasChar -> QFontEngineMultiFontConfig::shouldLoadFontEngineForCharacter -> QFontEngineMulti::stringToCMap -> QTextEngine::shapeText -> QQuickTextPrivate::setupTextLayout -> QQuickLabel::componentComplete -> PlasmaQuick::SharedQmlEngine::completeInitialization -> Klipper::Klipper -> Klipper::self Same font-match anomaly, still present after `fc-cache -r`: $ fc-match sans KaTeX_AMS-Regular.woff: "Noto Sans" "<unknown style>" $ fc-match -v sans | grep -E 'file|fontversion' file: "/usr/share/fonts/truetype/katex/KaTeX_AMS-Regular.woff" fontversion: 2147483647 Extra data: the bad entries are only in the USER cache. With an empty XDG_CACHE_HOME (system cache only) `fc-match sans` correctly returns NotoSans-Regular.ttf; with ~/.cache/fontconfig it returns the KaTeX .woff. `fc-list` shows the KaTeX .woff/.woff2 files cached with empty family/charset/fontversion, while `fc-query` on the same files returns family=KaTeX_AMS, fontversion=65536 and a valid charset. So fontconfig 2.17.1 generates malformed cache entries for these WOFF files, and Qt then crashes in FcCharSetHasChar on the malformed pattern. `fc-cache -r` stopped the loop (stable 30+ min), but since `fc-match sans` still returns the KaTeX .woff, I expect recurrence until fonts-katex is removed. Can confirm a test package if needed. -- 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
