Public bug reported:
Kubuntu 26.04, Plasma 6.6.x, X11.
Plasma and Konsole repeatedly crashed with SIGSEGV inside:
libfontconfig.so.1 -> FcCharSetHasChar -> QFontEngineMultiFontConfig
Before removing fonts-katex:
fc-match sans-serif
returned:
KaTeX_AMS-Regular.woff: "Noto Sans" "<unknown style>"
KaTeX_AMS-Regular.woff belonged to package fonts-katex and was located in:
/usr/share/fonts/truetype/katex/
Both plasmashell and konsole crashed in FcCharSetHasChar.
After:
apt remove fonts-katex
fc-cache -f -v
fc-match sans-serif
now returns:
NotoSans-Regular.ttf: "Noto Sans" "Regular"
Plasma and Konsole no longer crash, including after locking/unlocking the
Plasma X11 session.
fonts-katex was installed as part of the Kubuntu desktop package installation,
not manually.
Expected behavior:
fc-match sans-serif should resolve to a normal sans-serif font such as Noto
Sans, and Plasma/Konsole should not crash.
Actual behavior:
With fonts-katex installed, fc-match sans-serif resolved to
KaTeX_AMS-Regular.woff and Plasma/Konsole crashed with SIGSEGV in
FcCharSetHasChar.
Steps to reproduce:
1. Have fonts-katex installed.
2. Run: fc-match sans-serif
3. Observe KaTeX_AMS-Regular.woff being selected.
4. Start/use Plasma or Konsole.
5. SIGSEGV occurs in libfontconfig.so.1 -> FcCharSetHasChar.
Workaround:
sudo apt remove fonts-katex
sudo fc-cache -f -v
ProblemType: Bug
DistroRelease: Ubuntu 26.04
Package: fonts-katex (not installed)
ProcVersionSignature: Ubuntu 7.0.0-34.34-generic 7.0.14
Uname: Linux 7.0.0-34-generic x86_64
ApportVersion: 2.34.1-0ubuntu0.1
Architecture: amd64
CasperMD5CheckResult: unknown
CurrentDesktop: KDE
Date: Wed Sep 30 20:50:19 2026
InstallationDate: Installed on 2026-09-16 (14 days ago)
InstallationMedia: Kubuntu 26.04.1 LTS "Resolute Raccoon" - Release amd64
(20260826.1)
SourcePackage: node-katex
UpgradeStatus: No upgrade log present (probably fresh install)
** Affects: node-katex (Ubuntu)
Importance: Undecided
Status: New
** Tags: amd64 apport-bug resolute
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https://bugs.launchpad.net/bugs/2169099
Title:
fonts-katex causes Fontconfig to select KaTeX_AMS-Regular.woff for
sans-serif, leading to SIGSEGV in Plasma and Konsole
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