CVE-2026-63276
Announced: Sep 21, 2026
Fixed in: LibreOffice 26.2.5
Description:
LibreOffice converts CFF fonts to Type 1 when it subsets a font, which happens when a document is exported to PDF, and CFF fonts may be embedded in documents.
A stack buffer overflow existed in that conversion. The converted operators were written into a fixed size buffer with no check that they still fit, so a glyph emitting many operators wrote past the end of the buffer.
In fixed versions the remaining capacity is tracked and the conversion stops when it is used up.
All users are recommended to upgrade to LibreOffice >= 26.2.5 to avoid this problem.
Credits:
Thanks to Claude and Ada Logics – found by Anthropic using agents to study the security of open-source projects, with Ada Logics validating and reporting.
Thanks to Caolán McNamara of Collabora Productivity for providing the fix.
References:
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