Bug 2450791 (CVE-2026-27651)

Summary: CVE-2026-27651 NGINX: NGINX: Denial of Service via undisclosed requests when ngx_mail_auth_http_module is enabled
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: high Docs Contact:
Priority: high    
Version: unspecifiedKeywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in NGINX, specifically within the ngx_mail_auth_http_module. When this module is enabled, and CRAM-MD5 or APOP authentication is active with an authentication server that permits retries, undisclosed requests can cause NGINX worker processes to terminate. This can lead to a Denial of Service (DoS), making the affected NGINX instance unavailable to legitimate users.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Bug Depends On: 2450834, 2450837, 2450838, 2450839    
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Description OSIDB Bzimport 2026-03-24 15:02:57 UTC
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.