# CVE-2026-128339: ExcelJS through 4.4.0 Memory Exhaustion via Oversized Merged Cell Range

Status: published. Published: 2026-11-13. Updated: 2026-11-13.

ExcelJS through 4.4.0 contains a memory exhaustion vulnerability in Worksheet._parseMergeCells that allows attackers to crash applications by supplying unbounded mergeCell ranges. Attackers can craft a small workbook with a mergeCell ref like A1:XFD1048576, causing xlsx.load() to create billions of Row and Cell objects and abort the process.

## Remediation

- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: VulnCheck) — https://github.com/exceljs/exceljs/pull/3114

## Affected products and versions

- exceljs / exceljs (exceljs): ≥ 0; ≤ 4.4.0 (affected, semver). Source: CNA: VulnCheck

## Severity and prioritization

- CVSS 4.0: 8.7 (high); CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N; source: CNA: VulnCheck

- CVSS 3.1: 7.5 (high); CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H; source: CNA: VulnCheck

- CVSS 4.0: 8.7 (high); CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/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; source: NVD: disclosure@vulncheck.com

- CVSS 3.1: 7.5 (high); CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H; source: NVD: disclosure@vulncheck.com

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: Not available

- Weaknesses: CWE-770

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/exceljs/exceljs (CNA: VulnCheck; product)

- https://github.com/mateocallec/exceljs-hardened/security/advisories/GHSA-wh3v-83h4-rwwq (CNA: VulnCheck; third-party-advisory)

- https://github.com/exceljs/exceljs/blob/v4.4.0/lib/doc/worksheet.js#L613-L632 (CNA: VulnCheck; technical-description)

- https://github.com/exceljs/exceljs/blob/v4.4.0/lib/doc/worksheet.js#L895-L901 (CNA: VulnCheck; technical-description)

- https://github.com/exceljs/exceljs/issues/3107 (CNA: VulnCheck; issue-tracking)

- https://github.com/exceljs/exceljs/pull/3114 (CNA: VulnCheck; issue-tracking, patch)

- https://www.vulncheck.com/advisories/exceljs-through-4.4.0-memory-exhaustion-via-oversized-merged-cell-range (CNA: VulnCheck; third-party-advisory)

- https://github.com/exceljs/exceljs (disclosure@vulncheck.com)

- https://github.com/exceljs/exceljs/blob/v4.4.0/lib/doc/worksheet.js#L613-L632 (disclosure@vulncheck.com)

- https://github.com/exceljs/exceljs/blob/v4.4.0/lib/doc/worksheet.js#L895-L901 (disclosure@vulncheck.com)

- https://github.com/exceljs/exceljs/issues/3107 (disclosure@vulncheck.com)

- https://github.com/exceljs/exceljs/pull/3114 (disclosure@vulncheck.com)

- https://github.com/mateocallec/exceljs-hardened/security/advisories/GHSA-wh3v-83h4-rwwq (disclosure@vulncheck.com)

- https://www.vulncheck.com/advisories/exceljs-through-4.4.0-memory-exhaustion-via-oversized-merged-cell-range (disclosure@vulncheck.com)

## Provenance

- CNA: VulnCheck: https://www.cve.org/CVERecord?id=CVE-2026-128339; retrieved 2026-11-13; source updated 2026-11-13

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-128339; retrieved 2026-11-13; source updated 2026-11-13

Revision: 20d7f6fa902c0014048a2848c483c50dfc33781888125ff5326c63db346327f6

Canonical: https://y2.dev/cve/CVE-2026-128339

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