CVE-2026-128343 json
ExcelJS through 4.4.0 Denial of Service via Oversized Row Number
published 29d ago modified 17h ago also EUVD-2026-125156 , GHSA-3gm5-qxj8-89rr
Unreviewed: the maintainers' own advisory
Published by the maintainers on their GitHub repository mateocallec/exceljs-hardened. GitHub has not reviewed it into the GitHub Advisory Database, so the affected packages and versions are the maintainers' word. Read the full advisory on GitHub.
- cvss
- 7.5
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.7%
- EPSS 0.7% chance of exploitation in 30 days, percentile 52%
- public exploits
- 0
- none known
Summary
exceljs through 4.4.0 contains a denial of service vulnerability that allows attackers to block the event loop by supplying unbounded row r attributes parsed in row-xform.js. Attackers can craft an XLSX file with a row numbered far beyond Excel's limit, making getSheetValues(), workbook writes and CSV export consume time proportional to that number.
Patch / fix
- npm exceljs-hardened 5.1.0
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Check with FencerCISA SSVC
- Exploitation
- none
- Automatable
- yes
- Technical impact
- partial
- Assessed
- yesterday
Exploit prediction
0.68% chance of exploitation in the next 30 days, higher than 52% of all scored CVEs (FIRST EPSS, 2026-11-14).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 4.0 | 8.7 | 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 |
| CNA | 3.1 | 7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
| CNA | 4.0 | 8.7 | 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 |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| npm | exceljs-hardened | <=5.0.2 |
5.1.0 |
Affected products
- exceljs exceljs
Classification
- Weakness
-
- CWE-606 Unchecked Input for Loop Condition
References
-
github.com
/exceljs/exceljs
product
-
github.com
/mateocallec/exceljs-hardened/security/advisories/GHSA-3gm5-qxj8-89rr
third-party-advisory, advisory
-
github.com
/exceljs/exceljs/blob/v4.4.0/lib/xlsx/xform/sheet/row-xform.js#L73-L77
technical-description
-
github.com
/exceljs/exceljs/blob/v4.4.0/lib/doc/worksheet.js#L886-L893
technical-description
-
github.com
/exceljs/exceljs/blob/v4.4.0/lib/doc/worksheet.js#L571-L580
technical-description
-
vulncheck.com
/advisories/exceljs-through-4.4.0-denial-of-service-via-oversized-row-number
third-party-advisory
Sources
- CVE List CVE-2026-128343
- NVD CVE-2026-128343
- Maintainer advisory GHSA-3gm5-qxj8-89rr
Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.
The maintainers of mateocallec/exceljs-hardened published their own advisory on GitHub. Reviewed sources take precedence over it.