Vulnerability Details 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. 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.
Exploit prediction scoring system (EPSS) score
EPSS Score 0.0
EPSS Ranking 11.8%
CVSS Severity
CVSS v3 Score 7.5
Products affected by CVE-2026-27651
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cpe:2.3:a:f5:nginx_open_source:*
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cpe:2.3:a:f5:nginx_open_source:1.25.0
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cpe:2.3:a:f5:nginx_open_source:1.25.1
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cpe:2.3:a:f5:nginx_open_source:1.25.2
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cpe:2.3:a:f5:nginx_open_source:1.25.3
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cpe:2.3:a:f5:nginx_open_source:1.25.4
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cpe:2.3:a:f5:nginx_open_source:1.26.1
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cpe:2.3:a:f5:nginx_open_source:1.26.2
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cpe:2.3:a:f5:nginx_open_source:1.27.0
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cpe:2.3:a:f5:nginx_open_source:1.28.2
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cpe:2.3:a:f5:nginx_open_source:1.29.0
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cpe:2.3:a:f5:nginx_open_source:1.29.5
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cpe:2.3:a:f5:nginx_open_source:1.3.0
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cpe:2.3:a:f5:nginx_open_source:1.5.13
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cpe:2.3:a:f5:nginx_plus:r32
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cpe:2.3:a:f5:nginx_plus:r33
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cpe:2.3:a:f5:nginx_plus:r34
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cpe:2.3:a:f5:nginx_plus:r35
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cpe:2.3:a:f5:nginx_plus:r36