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Fencer Vulns
medium 5.4

CVE-2026-63276 json

Stack buffer overflow in CFF to Type 1 font conversion

published 2026-09-22 47 d ago modified 2026-09-22 47 d ago also EUVD-2026-84356

cvss
5.4
version 4.0, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 9%
public exploits
0
none known

Summary

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.

Patch / fix

  • The Document Foundation LibreOffice < 26.2.5
  • libreoffice Debian 13 4:25.2.3-2+deb13u7
  • libreoffice Debian 14 4:26.2.5.2-1

debian advisories DEBIAN-CVE-2026-63276

  • libreoffice Ubuntu 22.04 LTS 1:7.3.7-0ubuntu0.22.04.13
  • libreoffice Ubuntu 24.04 LTS 4:24.2.7-0ubuntu0.24.04.7
  • libreoffice Ubuntu 26.04 LTS 4:26.2.6.3-0ubuntu0.26.04.2

ubuntu advisories UBUNTU-CVE-2026-63276

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • libreoffice RHEL 9 1:7.1.8.1-15.el9_8.3
  • autocorr-af RHEL 9 1:7.1.8.1-15.el9_8.3
  • autocorr-bg RHEL 9 1:7.1.8.1-15.el9_8.3
  • autocorr-ca RHEL 9 1:7.1.8.1-15.el9_8.3
  • autocorr-cs RHEL 9 1:7.1.8.1-15.el9_8.3
  • autocorr-da RHEL 9 1:7.1.8.1-15.el9_8.3
  • autocorr-de RHEL 9 1:7.1.8.1-15.el9_8.3
  • autocorr-el RHEL 9 1:7.1.8.1-15.el9_8.3

red hat advisories RHSA-2026:82013

  • sac AlmaLinux 8 1.3-29.el8_10
  • flute AlmaLinux 8 1.3.0-19.OOo31.el8_10
  • libbase AlmaLinux 8 1.1.3-21.el8_10
  • libfonts AlmaLinux 8 1.1.3-23.el8_10
  • liblayout AlmaLinux 8 0.2.10-19.el8_10
  • libloader AlmaLinux 8 1.1.3-19.el8_10
  • libformula AlmaLinux 8 1.1.3-20.el8_10
  • autocorr-af AlmaLinux 8 1:7.1.8.1-3.el8_10.alma.1

almalinux advisories ALSA-2026:88164ALSA-2026:82013

  • flute Rocky Linux 8 1.3.0-19.OOo31.el8_10
  • libbase Rocky Linux 8 1.1.3-21.el8_10
  • libfonts Rocky Linux 8 1.1.3-23.el8_10
  • liblayout Rocky Linux 8 0.2.10-19.el8_10
  • libloader Rocky Linux 8 1.1.3-19.el8_10
  • libformula Rocky Linux 8 1.1.3-20.el8_10
  • libreoffice Rocky Linux 8 1:7.1.8.1-3.el8_10
  • librepository Rocky Linux 8 1.1.3-19.el8_10

rocky linux advisories RLSA-2026:88164RLSA-2026:82013

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-63276 updated cvss 7.3

libreoffice: stack buffer overflow in CFF to Type 1 font conversion

  • Red Hat Enterprise Linux 6 autocorr-af, autocorr-bg, autocorr-ca, autocorr-cs, autocorr-da, autocorr-de, +60 more
    affected: workaround, no fix planned “Do not export documents from unknown or untrusted sources to PDF with LibreOffice.”
  • Red Hat Enterprise Linux 7 autocorr-af, autocorr-bg, autocorr-ca, autocorr-cs, autocorr-da, autocorr-de, +105 more
    affected: workaround, no fix available “Do not export documents from unknown or untrusted sources to PDF with LibreOffice.”
  • Red Hat Enterprise Linux AppStream (v. 8) sac 1.3-29.el8_10, libbase 1.1.3-21.el8_10, libfonts 1.1.3-23.el8_10, libloader 1.1.3-19.el8_10, libformula 1.1.3-20.el8_10, liblayout 0.2.10-19.el8_10, +107 more
    fixed: vendor fix “Do not export documents from unknown or untrusted sources to PDF with LibreOffice.” RHSA-2026:88164
  • Red Hat Enterprise Linux AppStream (v. 9) autocorr-af 7.1.8.1-15.el9_8.3, autocorr-bg 7.1.8.1-15.el9_8.3, autocorr-ca 7.1.8.1-15.el9_8.3, autocorr-cs 7.1.8.1-15.el9_8.3, autocorr-da 7.1.8.1-15.el9_8.3, autocorr-de 7.1.8.1-15.el9_8.3, +100 more Red Hat Enterprise Linux CodeReady Linux Builder (v. 9) libreoffice-sdk 7.1.8.1-15.el9_8.3
    fixed: vendor fix “Do not export documents from unknown or untrusted sources to PDF with LibreOffice.” RHSA-2026:82013
  • Red Hat Enterprise Linux CRB (v. 8) libreoffice-sdk 7.1.8.1-3.el8_10
    fixed: vendor fix “Do not export documents from unknown or untrusted sources to PDF with LibreOffice.” RHSA-2026:88164

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
47 d ago

Exploit prediction

0.19% chance of exploitation in the next 30 days, higher than 9% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 4.0 5.4 CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:L/VI:L/VA:H/SC:N/SI:N/SA:N/E:P
CNA 4.0 5.4 CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:L/VI:L/VA:H/SC:N/SI:N/SA:N/E:P/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Affected products

  • The Document Foundation LibreOffice

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.