CVE-2026-40701 NGINX ngx_http_ssl_module vulnerability
An unauthenticated attacker can trigger a heap-use-after-free in NGINX when specific SSL verification and OCSP settings are enabled, causing data modification or service restart.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-40701?
CVE-2026-40701 is a medium-severity use after free vulnerability in F5 NGINX Open Source, published on 13 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_ssl_module module when the ssl_verify_client directive is set to "on" or "optional," and the ssl_ocsp directive is set to "on" or the leaf parameters are configured with a resolver. With this configuration, an unauthenticated attacker can send requests along with conditions beyond its control that may cause a heap-use-after-free error in the NGINX worker process. This vulnerability may result in limited modification of data or the NGINX worker process restarting.
Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.
Weakness: CWE-416
Which versions are affected by CVE-2026-40701?
2 open source packages ship an affected version, including nginx and nginx-gateway. It affects 7 products.
| Package | Affected | Fixed in |
|---|---|---|
nginx Bitnami | From 1.19.0 | 1.30.1 |
nginx-gateway Bitnami | From 1.19.0 | 1.30.1 |
Products include F5 Dos, F5 Nginx Gateway Fabric, F5 Nginx Ingress Controller, F5 Nginx Instance Manager, F5 Nginx Open Source, F5 Nginx Plus and 1 more.
How do I fix CVE-2026-40701?
Upgrade nginx to 1.30.1 or later.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2026-40701 being exploited?
There is no known exploitation of CVE-2026-40701 in the wild and no public exploit code.
Public exploit code: 1 proofs of concept on GitHub.
Other vulnerabilities in F5 NGINX Open Source
- CVE-2026-42055 NGINX ngx_http_proxy_v2_module and ngx_http_grpc_module vulnerability
- CVE-2026-42945 NGINX ngx_http_rewrite_module vulnerability
- CVE-2026-42946 NGINX ngx_http_scgi_module and ngx_http_uwsgi_module vulnerability
- CVE-2026-40460 NGINX ngx_quic_module vulnerability
- CVE-2026-48142 NGINX ngx_http_charset_module vulnerability
Sources
Also known as ALPINE-CVE-2026-40701, AZL-86850, BELL-CVE-2026-40701, BIT-nginx-2026-40701, BIT-nginx-gateway-2026-40701, DEBIAN-CVE-2026-40701 and 8 more.