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

Quick assessment

Affected
The Document Foundation LibreOffice
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

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

CVSS 5.4 · Medium

Affected Version Matrix 1

VendorProduct Version RangeStatus
The Document Foundation LibreOffice 26.2< < 26.2.5 affected
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I. Basic Information for CVE-2026-63276

Vulnerability Information

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Vulnerability Title
Stack buffer overflow in CFF to Type 1 font conversion
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
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
Source: CVE Program / CVE List V5
Vulnerability Type
跨界内存写
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
The Document Foundation LibreOffice 26.2 ~ < 26.2.5 -

II. Public POCs for CVE-2026-63276

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III. Intelligence Information for CVE-2026-63276

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Other References for CVE-2026-63276 (1)

Same Patch Batch · The Document Foundation · 2026-09-22 · 7 CVEs total

CVE-2026-63278 6.7 MEDIUM Package URLs can be used to exfiltrate arbitrary INI file values and environment variables
CVE-2026-63279 5.4 MEDIUM Out of bounds read in PICT image import
CVE-2026-63272 5.4 MEDIUM Heap buffer overflow in WMF text record import
CVE-2026-63274 5.4 MEDIUM Heap buffer overflow in PDF import stream handling
CVE-2026-63273 5.4 MEDIUM Heap buffer overflow in PDF import encryption handling
CVE-2026-63275 5.4 MEDIUM Stack buffer overflow in CFF font hint handling

IV. Related Vulnerabilities

Same product: LibreOffice
Same vendor: The Document Foundation
Same weakness: CWE-787

V. Comments for CVE-2026-63276

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