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PatchSiren cyber security CVE debrief

CVE-2026-6040 The Document Foundation CVE debrief

A heap use-after-free vulnerability existed in LibreOffice when importing the blank-width characters of an ODF number format. The issue occurred because a position value read from the document was not checked against the length of the format-code string. This allowed a malformed number format to be processed against memory outside that string. In fixed versions, the position is bounds-checked before use.

Vendor
The Document Foundation
Product
LibreOffice
CVSS
MEDIUM 5.4
CISA KEV
Not listed in stored evidence
Original CVE published
2026-06-15
Original CVE updated
2026-07-15
Advisory published
2026-06-15
Advisory updated
2026-07-15

Who should care

Users of LibreOffice, especially those who open documents from untrusted sources, should be aware of this vulnerability.

Technical summary

The vulnerability has a CVSS score of 5.4 and is classified as CWE-416 (Use After Free) and CWE-787 (Out-of-bounds Write).

Defensive priority

MEDIUM

Recommended defensive actions

  • Update to the latest version of LibreOffice to ensure the bounds-checking fix is applied.

Evidence notes

The CVE was published on June 15, 2026, and has a single reference to the LibreOffice security advisory.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-6040 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-6040

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-6040 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-6040

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.