CVE-2026-27651
HighCVSS 7.5Exploitation Probability (EPSS)
Elevated risk56th percentile - higher than 56% of all known CVEs
Summary
A vulnerability in the ngx_mail_auth_http_module of NGINX allows undisclosed requests to terminate worker processes. This occurs when CRAM-MD5 or APOP authentication is enabled and the authentication server permits retry via the Auth-Wait response header.
Risk Assessment
The risk involves potential termination of NGINX worker processes, leading to service unavailability for mail-related features and possible application disruption.
Recommendation
Immediately update NGINX to the latest patched version and temporarily disable the ngx_mail_auth_http_module if not required.
Other vulnerabilities in NGINX
See all- CVE-2016-1247High
The nginx package before 1.6.2-5+deb8u3 on Debian jessie and earlier versions on Ubuntu and Gentoo allow local users with access to the web server user account to gain root privileges via a symlink attack on the error log.
- CVE-2016-4450High
In nginx before 1.10.1 and 1.11.x before 1.11.1, a vulnerability allows remote attackers to cause a denial of service (NULL pointer dereference and worker process crash) via a crafted request, involving writing a client request body to a temporary file.
- CVE-2016-0742High
The resolver in nginx before 1.8.1 and 1.9.x before 1.9.10 allows remote attackers to cause a denial of service via an invalid pointer dereference, leading to a worker process crash.
- CVE-2014-0133High
Heap-based buffer overflow in the SPDY implementation in nginx 1.3.15 before 1.4.7 and 1.5.x before 1.5.12 allows remote attackers to execute arbitrary code via a crafted request.
- CVE-2026-9256High
A vulnerability in the ngx_http_rewrite_module of NGINX Plus and NGINX Open Source occurs when a rewrite directive uses a regex pattern with overlapping PCRE captures and a replacement string referencing multiple captures. An unauthenticated attacker can send crafted HTTP requests, causing a heap buffer overflow in the NGINX worker process, leading to a restart.
- CVE-2026-42945High
A vulnerability exists in NGINX Plus and NGINX Open Source within the ngx_http_rewrite_module. It occurs when the rewrite directive is followed by rewrite, if, or set directives and an unnamed PCRE capture (e.g., $1, $2) with a replacement string containing a question mark (?). An unauthenticated attacker can send crafted HTTP requests, causing a heap buffer overflow in the NGINX worker process, leading to a restart.
- CVE-2026-27654High
A vulnerability in the NGINX ngx_http_dav_module allows an attacker to trigger a buffer overflow in the NGINX worker process. The issue occurs when the configuration uses MOVE or COPY methods with alias directives and prefix locations.
- CVE-2016-0746Critical
A use-after-free vulnerability in the resolver in nginx versions 0.6.18 through 1.8.0 and 1.9.x before 1.9.10 allows remote attackers to cause a denial of service (worker process crash) or possibly have unspecified other impact via a crafted DNS response related to CNAME response processing.
- CVE-2026-60005High
A vulnerability exists in NGINX Plus and NGINX Open Source within the ngx_http_slice_module module. When the slice directive with unnamed regex captures is configured or during a background cache update, unauthenticated attackers can send requests causing uninitialized memory access in the NGINX worker process, leading to limited memory disclosure or a restart.
- CVE-2026-56434Medium
A vulnerability exists in NGINX Plus and NGINX Open Source within the ngx_http_ssi_module module. This issue occurs when Server-Side Includes (SSI), proxy_pass, and proxy_buffering off directives are configured. An unauthenticated attacker with man-in-the-middle (MITM) capability to control upstream server responses may trigger a use-after-free in the NGINX worker process.
Original NVD description (English source)
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.

