PatchSiren

PatchSiren cyber security CVE debrief

CVE-2026-40986 Spring CVE debrief

A medium-severity vulnerability, CVE-2026-40986, was found in Spring Web Flow's JavaScript RemotingHandler. The issue causes the body of an error response to be rendered as HTML, even when the response is not 'text/html'. This 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. The affected versions are Spring Web Flow 4.0.0, 3.0.0 through 3.0.1, and 2.5.0 through 2.5.1.

Vendor
Spring
Product
Spring Web Flow
CVSS
MEDIUM 4.8
CISA KEV
Not listed in stored evidence
Original CVE published
2026-06-11
Original CVE updated
2026-09-04
Advisory published
2026-06-11
Advisory updated
2026-09-04

Who should care

Users of Spring Web Flow 4.0.0, 3.0.0 through 3.0.1, and 2.5.0 through 2.5.1 should be aware of this vulnerability and take necessary actions to mitigate the risk.

Technical summary

The CVSS score for this vulnerability is 4.8, with a severity rating of MEDIUM. The vulnerability is caused by the JavaScript RemotingHandler rendering the body of an error response as HTML, even when the response is not 'text/html'. This can lead to a scripting attack in the user's browser if the error response contains error details with input reflected from an attacker.

Defensive priority

MEDIUM

Recommended defensive actions

  • Update to a non-vulnerable version of Spring Web Flow.
  • Implement proper input validation and error handling to prevent reflected input in error responses.

Evidence notes

The CVE record and NVD detail can be found at [cve-org] and [nvd], respectively. Additional information is available at [ref-4].

Sources and references

Verified primary and authoritative sources

  • CVE-2026-40986 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-40986

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-40986 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-40986

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.