CVE-2026-27651 remediation guide

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

When the ngx_mail_auth_http_module module is enabled on NGINX Plus or NGINX Open Source, undisclosed requests can cause worker processes to terminate. This issue may occur when (1) CRAM-MD5 or APOP authentication is enabled, and (2) the authentication server permits retry by returning the Auth-Wait response header. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

Open CVE record

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

Affected versions>= 1.29.0 < 1.29.7, >= 0.5.15 < 1.28.3, >= R36 < R36 P3, >= R35 < R35 P2, >= R34, >= R33, >= R32 < R32 P5, >= 0.5.15 <= 0.9.7, >= 1.0.0 < 1.28.3, >= r33 < r35, r32, r35, r36

Fixed versions1.28.3, 1.29.7, r35

Priority basisReview · CVSS 8.7 · EPSS 0.94%

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: >= 1.29.0 < 1.29.7, >= 0.5.15 < 1.28.3, >= R36 < R36 P3, >= R35 < R35 P2, >= R34, >= R33, >= R32 < R32 P5, >= 0.5.15 <= 0.9.7, >= 1.0.0 < 1.28.3, >= r33 < r35, r32, r35, r36. 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: 1.28.3, 1.29.7, r35. 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.