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="<name>" 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.
Published: 2026-11-10
Score: 4.8 Medium
EPSS: n/a
KEV: No
Impact: n/a
Action: n/a
AI Analysis

No analysis available yet.

Remediation

Vendor Solution

Users of affected versions should apply the following mitigation or upgrade.

Vendor Workaround

Escape or reject double quotes, backslashes and control characters in any file name that does not come from the application itself before passing it to DownloadEvent.setFileName or DownloadEvent.inline.

Tracking

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Advisories

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History

Tue, 10 Nov 2026 12:00:00 +0000

Type Values Removed Values Added
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="<name>" 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.
Title Unescaped Download File Name Allows Content-Disposition Parameter Injection in Vaadin Flow
Weaknesses CWE-116
References
Metrics cvssV4_0

{'score': 4.8, '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'}

Subscriptions

No data.

cve-icon MITRE

Status: PUBLISHED

Assigner: Vaadin

Published:

Updated: 2026-11-10T11:49:52.046Z

Reserved: 2026-11-01T13:24:59.528Z

Link: CVE-2026-120326

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Awaiting Analysis

Published: 2026-11-10T12:17:16.837

Modified: 2026-11-10T12:17:16.967

Link: CVE-2026-120326

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

No data.

Weaknesses
  • CWE-116

    Improper Encoding or Escaping of Output