VulnerabilityModified

CVE-2026-27651

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.

HIGH 8.7EPSS 0.94%

Does this matter?

High impact if exploited, but EPSS currently rates exploitation as unlikely (0.94%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.

Description

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 4.0: 8.7 HIGHCVSS: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/M
EPSS: 0.94% probability · 59th percentile
CISA KEV: Not listed
Weakness: CWE-476
Affected: f5/nginx open source · f5/nginx plus
Source: f5sirt@f5.com

References

Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.