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Vulnerability · Published May 13, 2026 · Assigned by f5

CVE-2026-40701NGINX ngx_http_ssl_module vulnerability

Medium 4.8

In plain English

A medium-severity use-after-free in NGINX Open Source from F5. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.7% (higher than 53% of all known vulnerabilities). Ready-made attack tooling exists: public proof-of-concept code. Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)4.8Medium
Exploit odds (30 days)0.7%top 47.0% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack tooling1Public PoC

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.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Alpine:v3.21nginx1.26.3-r1ALPINE-CVE-2026-40701
Alpine:v3.22nginx1.28.3-r1ALPINE-CVE-2026-40701
Alpine:v3.23nginx1.28.3-r1ALPINE-CVE-2026-40701
Debian:12nginx1.22.1-9+deb12u7DEBIAN-CVE-2026-40701
Debian:13nginx1.26.3-3+deb13u5DEBIAN-CVE-2026-40701
Debian:14nginx1.30.0-4DEBIAN-CVE-2026-40701
Ubuntu:22.04:LTSnginx1.18.0-6ubuntu14.12UBUNTU-CVE-2026-40701
Ubuntu:24.04:LTSnginx1.24.0-2ubuntu7.9UBUNTU-CVE-2026-40701
Ubuntu:25.10nginx1.28.0-6ubuntu1.4UBUNTU-CVE-2026-40701
Ubuntu:26.04:LTSnginx1.28.3-2ubuntu1.2UBUNTU-CVE-2026-40701

Affected products (as reported)

VendorProductVersions
F5 NGINX Plus R36 – before R36 P4R32 – before R32 P6
F5 NGINX Open Source 1.19.0 – before 1.30.1

Weakness: CWE-416 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:L

References