Heap-based buffer overflow in NGINX Plus and NGINX Open Source - CVE-2026-42533
Published: July 16, 2026
Vulnerability identifier: #VU137847
CSH Severity: High
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Amber
CVE-ID: CVE-2026-42533
CWE-ID: CWE-122
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: F5 Networks
Affected software:
NGINX Plus
NGINX Open Source
NGINX Plus
NGINX Open Source
Detailed vulnerability description
The vulnerability allows a remote attacker to execute arbitrary code or cause a denial of service.
The vulnerability exists due to heap-based buffer overflow in the map directive with regex matching when processing crafted HTTP requests that trigger regex capture variable references before the map output variable. A remote attacker can send crafted HTTP requests to execute arbitrary code or cause a denial of service.
Code execution is possible on systems with ASLR disabled or when ASLR can be bypassed. This is a data plane issue only.
How to mitigate CVE-2026-42533
Install security update from vendor's website.