CVE-2020-5397
MEDIUMCVE-2020-5397 is a medium-severity (CVSS 5.3) Cross-Site Request Forgery (CSRF) vulnerability in org.springframework:spring-webmvc. 1 public exploit reference exists, so weaponization risk is real. O3 Security confirms whether CVE-2020-5397 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
CSRF attack via CORS preflight requests with Spring MVC or Spring WebFlux
Real-World Exposure
org.springframework:spring-webmvc☕org.springframework:spring-webfluxReal-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 Framework, versions 5.2.x prior to 5.2.3 are vulnerable to CSRF attacks through CORS preflight requests that target Spring MVC (spring-webmvc module) or Spring WebFlux (spring-webflux module) endpoints. Only non-authenticated endpoints are vulnerable because preflight requests should not include credentials and therefore requests should fail authentication. However a notable exception to this are Chrome based browsers when using client certificates for authentication since Chrome sends TLS client certificates in CORS preflight requests in violation of spec requirements. No HTTP body can be sent or received as a result of this attack.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | org.springframework:spring-webmvc | ≥ 5.2.0&&< 5.2.3 | 5.2.3 |
| ☕Maven | org.springframework:spring-webflux | ≥ 5.2.0&&< 5.2.3 | 5.2.3 |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.springframework:spring-webmvc. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update org.springframework:spring-webmvc to 5.2.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-5397 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2020-5397 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2020-5397. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2020-5397 in your dependencies?
O3 detects CVE-2020-5397 across Maven dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.