CVE-2026-18329: NGINX ngx_http_js_module vulnerability
Description
NGINX JavaScript (njs) and QuickJS (qjs) engines have a vulnerability when a jsaccess handler performs asynchronous request body processing and an exception is thrown during asynchronous access-control evaluation before an explicit access denial is returned. An unauthenticated attacker can exploit this vulnerability by sending a crafted HTTP request that triggers an error condition in the access validation logic. This may cause the jsaccess phase to fail open, allowing the request to proceed instead of being denied, resulting in an authentication or authorization bypass and unauthorized access to protected resources.
Impact
This vulnerability may allow remote attackers to bypass jsaccess controls. There is no control plane exposure; this is a data plane issue only.
Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.
Event History
Frequently Asked Questions
Which deployments are exposed to this issue?
Only data plane deployments using js_access controls are affected. There is no control plane exposure described.
What does an attacker need to exploit it?
An unauthenticated attacker can send a crafted HTTP request that triggers an error in access validation logic. Exploitation involves asynchronous request body processing in a js_access handler and an exception during asynchronous access-control evaluation before an explicit denial is returned.
What is the likely outcome of successful exploitation?
The js_access phase can fail open, allowing a request to continue rather than be denied. This can bypass authentication or authorization controls and expose protected resources.
Are unsupported software versions covered by the assessment?
No. Software versions that have reached End of Technical Support are not evaluated.