PatchSiren

PatchSiren cyber security CVE debrief

CVE-2026-56746 netty CVE debrief

CVE-2026-56746 is a security control bypass vulnerability in Netty, a network application framework. The issue affects versions 4.2.0.Final through 4.2.15.Final and 4.1.0.Final through 4.1.135.Final. The vulnerability occurs in the CorsHandler's origin evaluation process, allowing an attacker to bypass security controls by sending a request with an Origin: null header. This bypasses the short-circuit mechanism designed to reject unauthorized cross-origin requests immediately. The issue is fixed in versions 4.1.136.Final and 4.2.16.Final. Users of affected versions should be aware of this vulnerability and take steps to upgrade to a patched version.

Vendor
netty
Product
Unknown
CVSS
MEDIUM 6.5
CISA KEV
Not listed in stored evidence
Original CVE published
2026-07-21
Original CVE updated
2026-07-22
Advisory published
2026-07-21
Advisory updated
2026-07-22

Who should care

Users of Netty versions 4.2.0.Final through 4.2.15.Final and 4.1.0.Final through 4.1.135.Final should be aware of this vulnerability and take steps to upgrade to a patched version. This includes operators, platform administrators, vulnerability management teams, and security teams who manage or use Netty in their applications.

Technical summary

The vulnerability is caused by a logical operator error in the origin evaluation process of the CorsHandler in Netty versions 4.2.0.Final through 4.2.15.Final and 4.1.0.Final through 4.1.135.Final. This allows an attacker to bypass the short-circuit mechanism by sending a request with an Origin: null header, forwarding unauthorized requests to the backend application and bypassing intended access controls. The issue is fixed in versions 4.1.136.Final and 4.2.16.Final. Affected users should review their deployments and upgrade to a patched version.

Defensive priority

Medium priority given the CVSS score of 6.5 and the potential for unauthorized access.

Recommended defensive actions

  • Upgrade to Netty version 4.1.136.Final or 4.2.16.Final
  • Review and update affected applications to use patched Netty versions
  • Monitor for suspicious cross-origin requests
  • Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up.
  • Review the supplied official advisory or CVE record to validate affected scope, severity, and vendor guidance.
  • Plan vendor-supported updates or mitigations through normal change control where exposure is confirmed.
  • Check relevant monitoring, detection, and logs for exposed assets that need extra review.

Evidence notes

Evidence is based on official CVE and NVD records, as well as source references from GitHub. The CVE record was published on 2026-07-21T22:17:14.667Z and last modified on 2026-07-22T20:35:40.827Z. The NVD entry is currently Awaiting Analysis. Limited source detail is available; defenders should verify affected scope and vendor guidance.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-56746 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-56746

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

  • CVE-2026-56746 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-56746

    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.