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NVD / CVE Program· CNA Document Fdn.

CVE-2026-63276: Stack buffer overflow in CFF to Type 1 font conversion

Noroxi assessment

Priority: Monitor (action score 21/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.19% (FIRST EPSS).
  • Someone with local access to the system can trigger it. No account or password is required. No special conditions are required; it is repeatable.
  • Fixed version: The Document Foundation LibreOffice < 26.2.5.

Low priority for now. Upgrade to The Document Foundation LibreOffice < 26.2.5 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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.

MediumCVSS 5.4 · v4.0—No exploit Fix available
Published
Sep 22, 2026
Updated
Sep 22, 2026
EPSS
0.1% · 9th percentile

Report tools

JSON

Action score

21

Monitor

Low priority for now.

CVSS
21 / 40 · 5.4 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.1%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · Document Fdn.
5.4
NVD has not scored this yet; the score shown is the CNA’s.

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

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2026-63276

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

—

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Document Fdn.). Independent of NVD's CPE analysis and usually ahead of it.

  • The Document Foundation LibreOffice

    • 26.2 and later · before < 26.2.5affected · 26.2 series

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
AlmaLinux:8autocorr-afbefore 1:7.1.8.1-3.el8_10.alma.11:7.1.8.1-3.el8_10.alma.1
AlmaLinux:8autocorr-bgbefore 1:7.1.8.1-3.el8_10.alma.11:7.1.8.1-3.el8_10.alma.1
AlmaLinux:8autocorr-cabefore 1:7.1.8.1-3.el8_10.alma.11:7.1.8.1-3.el8_10.alma.1
AlmaLinux:8autocorr-csbefore 1:7.1.8.1-3.el8_10.alma.11:7.1.8.1-3.el8_10.alma.1
AlmaLinux:8autocorr-dabefore 1:7.1.8.1-3.el8_10.alma.11:7.1.8.1-3.el8_10.alma.1
AlmaLinux:8autocorr-debefore 1:7.1.8.1-3.el8_10.alma.11:7.1.8.1-3.el8_10.alma.1
AlmaLinux:8autocorr-elbefore 1:7.1.8.1-3.el8_10.alma.11:7.1.8.1-3.el8_10.alma.1
AlmaLinux:8autocorr-enbefore 1:7.1.8.1-3.el8_10.alma.11:7.1.8.1-3.el8_10.alma.1
AlmaLinux:8autocorr-esbefore 1:7.1.8.1-3.el8_10.alma.11:7.1.8.1-3.el8_10.alma.1
AlmaLinux:8autocorr-fabefore 1:7.1.8.1-3.el8_10.alma.11:7.1.8.1-3.el8_10.alma.1
AlmaLinux:8autocorr-fibefore 1:7.1.8.1-3.el8_10.alma.11:7.1.8.1-3.el8_10.alma.1
AlmaLinux:8autocorr-frbefore 1:7.1.8.1-3.el8_10.alma.11:7.1.8.1-3.el8_10.alma.1
AlmaLinux:8autocorr-gabefore 1:7.1.8.1-3.el8_10.alma.11:7.1.8.1-3.el8_10.alma.1
AlmaLinux:8autocorr-hrbefore 1:7.1.8.1-3.el8_10.alma.11:7.1.8.1-3.el8_10.alma.1
AlmaLinux:8autocorr-hubefore 1:7.1.8.1-3.el8_10.alma.11:7.1.8.1-3.el8_10.alma.1
AlmaLinux:8autocorr-isbefore 1:7.1.8.1-3.el8_10.alma.11:7.1.8.1-3.el8_10.alma.1
AlmaLinux:8autocorr-itbefore 1:7.1.8.1-3.el8_10.alma.11:7.1.8.1-3.el8_10.alma.1
AlmaLinux:8autocorr-jabefore 1:7.1.8.1-3.el8_10.alma.11:7.1.8.1-3.el8_10.alma.1
AlmaLinux:8autocorr-kobefore 1:7.1.8.1-3.el8_10.alma.11:7.1.8.1-3.el8_10.alma.1
AlmaLinux:8autocorr-lbbefore 1:7.1.8.1-3.el8_10.alma.11:7.1.8.1-3.el8_10.alma.1
AlmaLinux:8autocorr-ltbefore 1:7.1.8.1-3.el8_10.alma.11:7.1.8.1-3.el8_10.alma.1
AlmaLinux:8autocorr-mnbefore 1:7.1.8.1-3.el8_10.alma.11:7.1.8.1-3.el8_10.alma.1
AlmaLinux:8autocorr-nlbefore 1:7.1.8.1-3.el8_10.alma.11:7.1.8.1-3.el8_10.alma.1
AlmaLinux:8autocorr-plbefore 1:7.1.8.1-3.el8_10.alma.11:7.1.8.1-3.el8_10.alma.1

+96

Same product

the document foundation: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-63277RCE via calcext:data-mappings, sql provider and jdbc connector
    34Monitor
  • CVE-2026-63266Arbitrary file write via calcext:data-mappings, sql provider and Firebird backup functionality
    27Monitor
  • CVE-2026-63270Environment/ini-file leaks
    26Monitor

Published before and after this one in the same product

  • ← EarlierCVE-2026-63274Sep 22, 2026 · Heap buffer overflow in PDF import stream handling
    21Monitor
  • ← EarlierCVE-2026-63275Sep 22, 2026 · Stack buffer overflow in CFF font hint handling
    21Monitor
  • Later →CVE-2026-63278Sep 22, 2026 · Package URLs can be used to exfiltrate arbitrary INI file values and environment variables
    26Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
The Document Foundation LibreOffice< 26.2.5Vendor (CNA)
almalinux:autocorr-af1:7.1.8.1-15.el9_8.3.alma.1 · AlmaLinux:9Package registry (OSV)
almalinux:autocorr-bg1:7.1.8.1-15.el9_8.3.alma.1 · AlmaLinux:9Package registry (OSV)
almalinux:autocorr-ca1:7.1.8.1-15.el9_8.3.alma.1 · AlmaLinux:9Package registry (OSV)
almalinux:autocorr-cs1:7.1.8.1-15.el9_8.3.alma.1 · AlmaLinux:9Package registry (OSV)
almalinux:autocorr-da1:7.1.8.1-15.el9_8.3.alma.1 · AlmaLinux:9Package registry (OSV)
almalinux:autocorr-de1:7.1.8.1-15.el9_8.3.alma.1 · AlmaLinux:9Package registry (OSV)
almalinux:autocorr-dsb1:7.1.8.1-15.el9_8.3.alma.1 · AlmaLinux:9Package registry (OSV)
almalinux:autocorr-el1:7.1.8.1-15.el9_8.3.alma.1 · AlmaLinux:9Package registry (OSV)
almalinux:autocorr-en1:7.1.8.1-15.el9_8.3.alma.1 · AlmaLinux:9Package registry (OSV)
almalinux:autocorr-es1:7.1.8.1-15.el9_8.3.alma.1 · AlmaLinux:9Package registry (OSV)
almalinux:autocorr-fa1:7.1.8.1-15.el9_8.3.alma.1 · AlmaLinux:9Package registry (OSV)
almalinux:autocorr-fi1:7.1.8.1-15.el9_8.3.alma.1 · AlmaLinux:9Package registry (OSV)
debian:libreoffice4:25.2.3-2+deb13u7 · Debian:13Package registry (OSV)
red hat:autocorr-af1:7.1.8.1-15.el9_8.3 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:autocorr-bg1:7.1.8.1-15.el9_8.3 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:autocorr-ca1:7.1.8.1-15.el9_8.3 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:autocorr-cs1:7.1.8.1-15.el9_8.3 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:autocorr-da1:7.1.8.1-15.el9_8.3 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:autocorr-de1:7.1.8.1-15.el9_8.3 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:autocorr-dsb1:7.1.8.1-15.el9_8.3 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:autocorr-el1:7.1.8.1-15.el9_8.3 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:autocorr-en1:7.1.8.1-15.el9_8.3 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:autocorr-es1:7.1.8.1-15.el9_8.3 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:autocorr-fa1:7.1.8.1-15.el9_8.3 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:autocorr-fi1:7.1.8.1-15.el9_8.3 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
rocky linux:flute0:1.3.0-19.OOo31.el8_10 · Rocky Linux:8Package registry (OSV)
rocky linux:libbase0:1.1.3-21.el8_10 · Rocky Linux:8Package registry (OSV)
rocky linux:libfonts0:1.1.3-23.el8_10 · Rocky Linux:8Package registry (OSV)
rocky linux:libformula0:1.1.3-20.el8_10 · Rocky Linux:8Package registry (OSV)

+7

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

  • CVE-2026-632730 days apartHeap buffer overflow in PDF import encryption handling
    21Monitor
  • CVE-2026-632750 days apartStack buffer overflow in CFF font hint handling
    21Monitor
  • CVE-2026-604799 days apartHeap buffer overflow in OOXML text box element import
    21Monitor
  • CVE-2026-835899 days apartHeap buffer overflow in spreadsheet tracked-changes import
    21Monitor

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Someone with local access to the system can trigger it.
  • No account or password is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
Integrity
Availability
Attack vector
Local
Attack complexity
Low
Privileges required
None
User interaction
P
Scope
X

Weakness class (CWE)

CWE-787 · Out-of-bounds Write

CVSS vector

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

nvd-secondary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records