Sources: National Vulnerability Database, CVE.org, CISA KEV, FIRST EPSS
CVE-2026-128346 Overview
ExcelJS through 4.4.0 contains a resource leak vulnerability in the streaming WorkbookReader.parse that leaves temporary files and open descriptors when sheet parsing fails or iteration stops early. Attackers can repeatedly upload malformed multi-sheet workbooks with worksheets placed before xl/sharedStrings.xml to fill the temporary directory and exhaust file descriptors.
Critical Impact
Affected Products
- ExcelJS: see the vendor advisory for the exact affected versions
Discovery Timeline
- 2026-11-13: CVE-2026-128346 published to the National Vulnerability Database by disclosure@vulncheck.com
- 2026-11-13: last updated in the NVD database
Technical Details for CVE-2026-128346
Vulnerability Analysis
CVE-2026-128346 is a Security Vulnerability weakness (CWE-459) in ExcelJS. Based on its CVSS vector, the flaw can be reached over the network, needs no login, and needs no user interaction.
With a CVSS base score of 8.7 and an EPSS exploitation probability of 0.63 percent, apply the vendor fix and confirm exposure on internet facing and business critical assets first.
Root Cause
The vendor description states: ExcelJS through 4.4.0 contains a resource leak vulnerability in the streaming WorkbookReader.parse that leaves temporary files and open descriptors when sheet parsing fails or iteration stops early. Attackers can repeatedly upload malformed multi-sheet workbooks with worksheets placed before xl/sharedStrings.xml to fill the temporary directory and exhaust file descriptors.
Attack Vector
Based on the CVSS vector, the flaw can be reached over the network, needs no login, and needs no user interaction. Attack complexity is low complexity.
No exploitation in the wild is confirmed by CISA at the time of the last update. Check the references below for any vendor or researcher proof of concept.
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
Detection Methods for CVE-2026-128346
Detection Strategies
- Inventory every instance of ExcelJS and compare the running version with the affected range above.
- Check external attack surface scans for internet facing instances of the component.
- Run an authenticated vulnerability scan once your scanner ships a check for this CVE.
Monitoring Recommendations
- Forward ExcelJS application, access and audit logs to your SIEM for retrospective hunting.
- Alert on new processes, configuration changes or outbound connections from the affected service.
- Track the vendor advisory and the CISA KEV catalog for changes in exploitation status.
How to Mitigate CVE-2026-128346
Immediate Actions Required
- Apply the fixed version of ExcelJS named in the vendor advisory.
- Prioritize internet facing and business critical instances first.
- Rescan after the change to confirm the exposure is closed.
Patch Information
Use the fixed version listed in the vendor advisory for ExcelJS.
Workarounds
- If patching must wait, restrict network access to the affected service and place it behind authentication or a web application firewall rule.
CWE References
Technical References
This entry is built directly from NVD, CISA KEV and EPSS data. Verify fixed versions in the vendor advisory before you deploy.
Frequently asked questions
Related CVEs
Multer is a node.js middleware for handling `multipart/form-data`. A vulnerability in Multer prior to version 2.1.0 allows an attacker to trigger a Denial of Service (DoS) by sending malformed requests, potentially causing resource exhaustion. Users should upgrade to version 2.1.0 to receive a patch. No known workarounds are available.
An Incomplete Cleanup vulnerability in the rpd process of Juniper Networks Junos OS and Junos OS Evolved allows a configured MVPN neighbor to cause a denial of service via a BGP MVPN update when an inter‑region segmented VRF with 'protocols mvpn inter-region-template' is configured.
Zebra before 7.0.0 contains an incomplete cleanup vulnerability that allows unauthenticated peers to stall initial sync by serving a forged checkpoint block body. Attackers can supply a body with forged authorizing data near the final checkpoint, leaving rejected hashes in the sent-hash set so the node stops requesting blocks until restart.
Missing MinIO policy cleanup on bucket deletion via Apache CloudStack allows users to retain access to buckets which they previously owned. If another user creates a new bucket with the same name, the previous owners can gain unauthorized read and write access to it by using the previously generated access and secret keys. Users are recommended to upgrade to Apache CloudStack versions 4.20.3.0 or 4.22.0.1, or later, which fixes this issue.
Earn your free CTEM certification.
Learn to scope, prioritize, validate and mobilize fixes for CVEs like CVE-2026-128346 with a free CTEM certification.
Beginner / Practitioner / Program Leader
Explore certifications