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Fencer Intel
medium 5.4

CVE-2026-63276 json

Stack buffer overflow in CFF to Type 1 font conversion

published last mo. modified last mo. 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

Is CVE-2026-63276 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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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-af 7.1.8.1-16.el9_9.1, autocorr-bg 7.1.8.1-15.el9_8.3, autocorr-bg 7.1.8.1-16.el9_9.1, autocorr-ca 7.1.8.1-15.el9_8.3, autocorr-ca 7.1.8.1-16.el9_9.1, +206 more Red Hat Enterprise Linux CodeReady Linux Builder (v. 9) libreoffice-sdk 7.1.8.1-15.el9_8.3, libreoffice-sdk 7.1.8.1-16.el9_9.1
    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
last mo.

Exploit prediction

0.20% chance of exploitation in the next 30 days, higher than 9% of all scored CVEs (FIRST EPSS, 2026-11-11).

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 Intel 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.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.