Security readout for executives and security teams
Plain-English summary
This vulnerability lets an attacker make affected Vaadin applications reflect malicious JavaScript through the default “route not found” error page. A victim must open a crafted URL. Impact is typical reflected XSS: possible session or data exposure in the victim’s browser, depending on application context.
Executive priority
Treat as a routine but timely remediation for public Vaadin applications. It is not KEV-listed and requires user interaction, but browser-side compromise can still affect customer trust and application data confidentiality.
Technical view
Vaadin Flow server lacked output sanitization in the default RouteNotFoundError view. Affected ranges are com.vaadin:flow-server 1.0.0-1.0.10 and 1.1.0-1.4.2, corresponding to Vaadin 10.0.0-10.0.13 and 11.0.0-13.0.5. CVSS 3.1 is 6.1: network exploitable, low complexity, no privileges, user interaction required, changed scope.
Likely exposure
Exposure is most likely in internet-facing Vaadin 10, 11, 12, or 13 applications using the default route-not-found error view from affected flow-server versions.
Exploitation context
The source bundle does not show active exploitation, and KEV is false. Exploitation requires social engineering or another path to make a user open a crafted URL. No source in the bundle supports unaided remote compromise.
Researcher notes
Focus validation on dependency versioning and default error-view behavior. The evidence supports reflected XSS from missing output sanitization, not stored XSS or server-side code execution. Do not assume exploit-in-the-wild status from the supplied sources.
Mitigation direction
- Upgrade Vaadin or flow-server to a version outside the affected ranges.
- Check Vaadin’s advisory for the vendor-supported fixed version path.
- Avoid using the vulnerable default RouteNotFoundError view in affected deployments.
- Review browser security headers as defense-in-depth, not as the primary fix.
Validation and detection
- Inventory Vaadin and com.vaadin:flow-server versions in application dependencies.
- Confirm whether the application uses the default RouteNotFoundError view.
- Review public routes that render route-not-found responses.
- Run regression tests for route-not-found pages after upgrading.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
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ATT&CK lookup starting points
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Open ATT&CK lookupCVE-2019-25027 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Medium
- CVSS
- 6.1 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N2.82.7Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
6.1MediumVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Source materials
- CVE List V5 sourceCVE List V5
- https://vaadin.com/security/cve-2019-25027CVE reference · x_refsource_MISC
- https://github.com/vaadin/flow/pull/5498CVE reference · x_refsource_MISC
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Improper Neutralization of Script in an Error Message Web Page
Improper Neutralization of Script in an Error Message Web Page represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.