CVE-2026-42945 remediation guide

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

NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_rewrite_module module. This vulnerability exists when the rewrite directive is followed by a rewrite, if, or set directive and an unnamed Perl-Compatible Regular Expression (PCRE) capture (for example, $1, $2) with a replacement string that includes a question mark (?). An unauthenticated attacker along with conditions beyond its control can exploit this vulnerability by sending crafted HTTP requests. This may cause a heap buffer overflow in the NGINX worker process leading to a restart. Additionally, attackers can execut...

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Research in progress

A verified fixed-version field is not available. Use the linked NVD and supporting references, then confirm the vendor-supported path before changing production systems.

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

Affected versions>= R36 < R36 P4, >= R32 < R32 P6, >= 0.6.27 < 1.30.1, >= 4.3.0 <= 4.7.0, 4.8.0, >= 1.3.0 <= 1.6.2, >= 2.0.0 <= 2.5.1, >= 3.5.0 <= 3.7.2, >= 4.0.0 <= 4.0.1, >= 5.0.0 <= 5.4.1, >= 2.16.0 <= 2.21.1, >= 0.6.27 <= 1.30.0, >= r32 <= r36, >= 4.9.0 <= 4.16.0, >= 5.1.0 <= 5.8.0, >= 5.9.0 <= 5.12.1

Fixed versionsNo verified fixed-version field is available yet

Priority basisPriority · CVSS 9.2 · EPSS 61.5%

Identify the affected asset

Confirm whether F5 NGINX Plus, NGINX Open Source, 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: >= R36 < R36 P4, >= R32 < R32 P6, >= 0.6.27 < 1.30.1, >= 4.3.0 <= 4.7.0, 4.8.0, >= 1.3.0 <= 1.6.2, >= 2.0.0 <= 2.5.1, >= 3.5.0 <= 3.7.2, >= 4.0.0 <= 4.0.1, >= 5.0.0 <= 5.4.1, >= 2.16.0 <= 2.21.1, >= 0.6.27 <= 1.30.0, >= r32 <= r36, >= 4.9.0 <= 4.16.0, >= 5.1.0 <= 5.8.0, >= 5.9.0 <= 5.12.1. Treat incomplete inventory results as unresolved.

Prioritize with independent signals

FIRST EPSS indicates an elevated probability of exploitation. 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: No verified fixed-version field is available yet. 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.