Use-after-free in NGINX Open Source - CVE-2026-42530
Published: June 18, 2026
Vulnerability identifier: #VU134863
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-2026-42530
CWE-ID: CWE-416
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: F5 Networks
Affected software:
NGINX Open Source
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 use-after-free in the ngx_http_v3_module when processing a specially crafted HTTP/3 session that reopens a QPACK encoder stream. A remote attacker can send a specially crafted HTTP/3 session to execute arbitrary code or cause a denial of service.
Exploitation requires NGINX Open Source to be configured to use the HTTP/3 QUIC module. Code execution is possible on systems with ASLR disabled or when ASLR can be bypassed. There is no control plane exposure; this is a data plane issue only.
How to mitigate CVE-2026-42530
Install security update from vendor's website.