Review reviewHigh

CVE-2026-27651

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.

CVSS: 8.7
EPSS: 0.94%
CISA KEV: Not listed
Published: 2026.03.25

PRIORITY ASSESSMENT

Review review

The CVSS severity warrants an early asset and exposure review.

Known exploitationNot established by KEV

Exploit probability0.94%

Technical severityCVSS 8.7

Vulnerability overview

Affected product and versions

Product: F5 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 versions: 1.28.3, 1.29.7, r35

Recommended response sequence

Confirm exposure before applying a vendor-supported change.

Full remediation guide

1
Identify
Confirm that F5 NGINX Open Source, NGINX Plus, Red Hat Enterprise Linux 10 and an affected version are present.
2
Prioritize
Combine exploitation signals with asset exposure and business criticality.
3
Remediate
Follow the vendor advisory or supported update path and preserve rollback options.
4
Verify
Recheck the version, service health, access paths, and relevant logs.

Technical data

CVSS vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
CWE: CWE-476