CVE-2026-128342 json
ExcelJS through 4.4.0 Denial of Service via Oversized Worksheet sheetId
published 29d ago modified 17h ago also EUVD-2026-125157 , GHSA-9vv6-5g3h-prg5
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
- 0.5%
- EPSS 0.5% chance of exploitation in 30 days, percentile 46%
- 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 an unbounded sheetId in xl/workbook.xml. Attackers can provide a workbook with a huge sheetId, making the sparse worksheet array walk stall worksheets, getWorksheet and writeBuffer for seconds.
Patch / fix
- npm exceljs-hardened 5.1.0
Is CVE-2026-128342 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.
Check with FencerExploit prediction
0.54% chance of exploitation in the next 30 days, higher than 46% 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 |
| NVD | 3.1 | 7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
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-9vv6-5g3h-prg5
third-party-advisory, advisory
-
github.com
/exceljs/exceljs/blob/v4.4.0/lib/doc/workbook.js#L200-L206
technical-description
-
github.com
/exceljs/exceljs/blob/v4.4.0/lib/doc/workbook.js#L119-L125
technical-description
-
vulncheck.com
/advisories/exceljs-through-4.4.0-denial-of-service-via-oversized-worksheet-sheetid
third-party-advisory
Sources
- CVE List CVE-2026-128342
- NVD CVE-2026-128342
- Maintainer advisory GHSA-9vv6-5g3h-prg5
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.