Spring Framework Security Filter Bypass in WebFlux Kotlin Router DSL

published 2026-06-09 5 mo ago modified 2026-07-30 3 mo ago also GHSA-vqgp-pf68-6947 , EUVD-2026-35335

cvss: 4.8; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.2%; EPSS 0.2% chance of exploitation in 30 days, percentile 5%
public exploits: 0; none known

Spring WebFlux applications may be vulnerable to a security bypass when using the Kotlin Router DSL.

Affected versions: Spring Framework 5.3.0 through 5.3.48.

Patch / fix

fixed in 1

Spring Spring Framework 5.3.49

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-41847 updated 2026-08-25 cvss 4.8

Spring Framework: Spring WebFlux applications: Security bypass when using Kotlin Router DSL

Red Hat Fuse 7 spring-webflux
affected: workaround, no fix available “This vulnerability only applies when using Kotlin Router DSL. Applications using Java-based routing are not affected.”

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation: none
Automatable: no
Technical impact: partial
Assessed: 5 mo ago (2026-06-09)

Exploit prediction

0.17% chance of exploitation in the next 30 days, higher than 5% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CNA	3.1	4.8	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N
NVD	3.1	5.3	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
GitHub	3.1	4.8	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N

Affected packages

ecosystem	package	affected	fixed in
maven	org.springframework:spring-webflux	<=5.3.39	no fix listed

Affected products

Spring Spring Framework

Classification

Weakness

CWE-284 Improper Access Control

Technology feeds

Spring rss critical rss

References

spring.io /security/cve-2026-41847
web, vendor-advisory
nvd.nist.gov /vuln/detail/CVE-2026-41847
advisory
github.com /spring-projects/spring-framework
package

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary