CVE-2026-42055 remediation guide

F5 NGINX Open Source, NGINX Plus, Red Hat Enterprise Linux 10

NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_proxy_v2_module and ngx_http_grpc_module modules. This vulnerability exists when the proxy_http_version to 2 or grpc_pass directives are used to proxy HTTP/2 traffic, the ignore_invalid_headers directive is set to off, and the large_client_header_buffers directive size is larger than 2 megabytes. A remote, unauthenticated attacker, along with conditions beyond their control, could send large headers while creating an upstream request. This may cause a heap-based buffer overflow in the NGINX worker process leading to a res...

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ProductF5 NGINX Open Source, NGINX Plus, Red Hat Enterprise Linux 10

Affected versions>= 1.13.10 < 1.31.2, >= 1.30.2 < 1.30.3, >= 37.0 < 37.0.2.1, >= R36 < R36 P6, 4.9.0, >= 4.3.0 <= 4.7.0, >= 4.10.0 <= 4.16.0, >= 5.2.0 <= 5.8.0, >= 1.3.0 <= 1.6.2, >= 2.0.0 < 2.6.4, >= 3.5.0 <= 3.7.2, >= 5.0.0 < 5.5.1, 4.0.0, 4.0.1, >= 2.17.0 <= 2.22.0, >= 1.30.0 < 1.30.3, 1.31.1, >= 37.0.0 <= 37.0.1, r3, r30

Fixed versions2.6.4, 5.5.1, 1.30.3

Priority basisReview · CVSS 9.2 · EPSS 4.04%

Identify the affected asset

Confirm whether F5 NGINX Open Source, NGINX Plus, Red Hat Enterprise Linux 10 is installed, record the deployed version and installation path, and identify exposed interfaces.

Record the product name, package or appliance identifier, and installed version.
Identify internet-facing, administrative, API, and internal access paths.
Preserve the pre-change configuration and relevant service logs.

Validate the affected-version match

Compare the deployed version with the affected range: >= 1.13.10 < 1.31.2, >= 1.30.2 < 1.30.3, >= 37.0 < 37.0.2.1, >= R36 < R36 P6, 4.9.0, >= 4.3.0 <= 4.7.0, >= 4.10.0 <= 4.16.0, >= 5.2.0 <= 5.8.0, >= 1.3.0 <= 1.6.2, >= 2.0.0 < 2.6.4, >= 3.5.0 <= 3.7.2, >= 5.0.0 < 5.5.1, 4.0.0, 4.0.1, >= 2.17.0 <= 2.22.0, >= 1.30.0 < 1.30.3, 1.31.1, >= 37.0.0 <= 37.0.1, r3, r30. Treat incomplete inventory results as unresolved.

Prioritize with independent signals

The CVSS severity warrants an early asset and exposure review. Combine this signal with asset criticality, exposure, compensating controls, and business impact.

Apply supported remediation

Follow the vendor advisory or supported update path. Current fixed-version status: 2.6.4, 5.5.1, 1.30.3. Preserve configuration and rollback material before change.

Verify the result

Confirm the resulting version, service health, authentication and access paths, monitoring coverage, and relevant security logs.

Confirm the expected version and package state.
Run a functional health check for critical service paths.
Review authentication, error, application, and security monitoring logs.
Reassess exposure if the supported fix cannot be applied.

Operational boundary

This page does not replace the vendor advisory, support contract, change-management process, or recovery plan. Do not infer that an asset is unaffected from an incomplete inventory query or a missing fixed-version field.