Use-after-free in NGINX ngx_http_ssl_module OCSP resolver handling
CVE-2026-40701 is a use-after-free vulnerability in NGINX Plus and NGINX Open Source within ngx_http_ssl_module. The issue is triggered in configurations where client certificate verification is enabled via ssl_verify_client set to "on" or "optional," and OCSP handling is enabled via ssl_ocsp set to "on" or where leaf parameters are configured with a resolver. Available supporting content indicates the flaw occurs in asynchronous OCSP DNS resolution handling: if a TLS connection closes before asynchronous OCSP DNS resolution completes, the associated context pool can be destroyed without cancelling the outstanding resolver request. Subsequent resolver processing can then dereference freed heap memory in the NGINX worker process, causing a heap use-after-free condition.
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Exploits
No valid public exploits. Mallory filtered out 3 candidates as fakes, detection scripts, or README-only repos.
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Recent activity
12 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A medium-severity use-after-free vulnerability in NGINX ngx_http_ssl_module involving asynchronous OCSP DNS resolution after TLS connection closure.
A use-after-free vulnerability in NGINX ngx_http_ssl_module that may allow limited data modification or worker restart when specific client verification and OCSP settings are enabled.
A use-after-free vulnerability in NGINX ngx_http_ssl_module that can permit limited data modification or worker process restart when specific SSL client verification and OCSP settings are enabled.
A use-after-free vulnerability in NGINX asynchronous OCSP DNS resolution handling.
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