CVE-2026-40986 — spring-webflow
MEDIUMCVE-2026-40986 is a medium-severity (CVSS 4.8) Cross-site Scripting (XSS) vulnerability in org.springframework.webflow:spring-webflow. A fix is available for org.springframework.webflow:spring-webflow — see the affected versions and patch details below.
Spring Web Flow JS RemotingHandler renders non-HTML Response as HTML
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-40986.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2026-40986 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 382,574 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
org.springframework.webflow:spring-webflow☕org.springframework.webflow:spring-webflow☕org.springframework.webflow:spring-webflowReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.
Description
Spring Web Flow's JavaScript RemotingHandler renders the body of an error response as HTML even when the response is not "text/html", which can result in a scripting attack in the user's browser if the error response from the server contains error details with input reflected from an attacker.
Affected versions: Spring Web Flow 4.0.0; 3.0.0 through 3.0.1; 2.5.0 through 2.5.1.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | org.springframework.webflow:spring-webflow | ≥ 4.0.0&&< 4.0.1 | 4.0.1org.springframework.webflow:spring-webflow:4.0.1 |
| ☕Maven | org.springframework.webflow:spring-webflow | ≥ 3.0.0&&< 3.0.2 | 3.0.2org.springframework.webflow:spring-webflow:3.0.2 |
| ☕Maven | org.springframework.webflow:spring-webflow | all versions | No fix |
Affected Products
spring web flowbroadcomDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.springframework.webflow:spring-webflow, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update org.springframework.webflow:spring-webflow to 4.0.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-40986 is resolved across your whole dependency graph.
Workarounds
Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.
Frequently Asked Questions
Is CVE-2026-40986 in your dependencies?
Find it across Maven, including transitive dependencies.