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PatchSiren cyber security CVE debrief

CVE-2026-8357 The Document Foundation CVE debrief

CVE-2026-8357 is a medium-severity vulnerability in LibreOffice Calc that can cause a heap buffer overflow when compiling a very long formula made up of many opening tokens. The array that tracks nesting depth was allocated one element too small for the worst-case scenario, allowing the formula to write one element past its end. In fixed versions, the array is sized to hold the largest possible nesting depth.

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
2026-07-28
Advisory published
2026-06-15
Advisory updated
2026-07-28

Who should care

Users of LibreOffice Calc, particularly those who open spreadsheets from untrusted sources, should be aware of this vulnerability and ensure they are running a fixed version.

Technical summary

The vulnerability exists in the way LibreOffice Calc compiles cell formulas when opening a spreadsheet. A heap buffer overflow occurs when compiling a very long formula made up of many opening tokens. The array that tracks nesting depth was allocated one element too small for the worst-case scenario, allowing the formula to write one element past its end.

Defensive priority

Medium

Recommended defensive actions

  • Update to a fixed version of LibreOffice Calc
  • Be cautious when opening spreadsheets from untrusted sources

Evidence notes

The CVE record and NVD detail can be found at [cve-org] and [nvd], respectively. Additional information is available at [ref-4].

Sources and references

Verified primary and authoritative sources

  • CVE-2026-8357 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-8357

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

  • CVE-2026-8357 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-8357

    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.