CVE-2026-63276 Stack buffer overflow in CFF to Type 1 font conversion
A stack buffer overflow in LibreOffice's CFF to Type 1 font conversion allows attackers to execute arbitrary code or cause a crash via malicious documents.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-63276?
CVE-2026-63276 is a medium-severity memory corruption vulnerability in The Document Foundation LibreOffice, published on 22 Sep 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Official 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.
Weakness: CWE-787
Which versions are affected by CVE-2026-63276?
How do I fix CVE-2026-63276?
Apply the vendor's patch.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-63276 being exploited?
There is no known exploitation of CVE-2026-63276 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-63276, ECHO-5352-3f6e-0c72, GHSA-3xpv-4h8q-pj26, MINI-mhqq-m3gr-8vvh, UBUNTU-CVE-2026-63276.