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CVE-2026-42530

F5 Nginx•HIGH · CVSS 8.1•No exploitation reported

What is CVE-2026-42530?

NGINX Open Source has a vulnerability in the ngx_http_v3_module module. When NGINX Open Source is configured to use the HTTP/3 QUIC module, a remote unauthenticated attacker along with conditions beyond their control can use a specially crafted HTTP/3 session to reopen a QPACK encoder stream. This may cause a Use-after-Free in the NGINX worker process leading to a restart. Additionally, attackers can execute code on systems with Address Space Layout Randomization (ASLR) disabled or when the attacker can bypass ASLR. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

CVSS8.1 NVD 3.1

SeverityHIGH

ExploitationNo exploitation reported

EPSS6% · P94

Triage statusNo Known Exploit

ActionPatch this week

CVSS vectorCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

CWECWE-416

NVD published2026-06-17

NVD last modified2026-10-26

Timeline

2026-06-17Published to the U.S. National Vulnerability Database (NVD)
2026-06-19First covered in a defend.network daily briefing
2026-10-26NVD record last updated

Affected product

F5 Nginx

NVD also lists CPE entries for: F5 Nginx Gateway Fabric, F5 Nginx Ingress Controller, F5 Nginx Instance Manager, F5 Nginx Open Source

Remediation Steps

Apply the vendor security update for F5 NGINX Open Source as a priority.
Restrict network exposure of the affected service to trusted sources until patched.
Review logs and detections for indicators of exploitation.
Confirm fixed versions against the official vendor advisory before deploying.

References

Referenced in our briefings & reports

Vulnerability Priority Report – Week 3 of June 2026 (June 15 – 21)
NGINX RCE, Windows crypto-stealer, Salesforce breaches, INC ransomware surge (2026-06-19)

Related vulnerabilities

CVE-2026-42945 – F5 Nginx (same product)
CVE-2026-94127 – F5 BIG-IP APM (same vendor)
CVE-2025-53521 – F5 BIG-IP (same vendor)
CVE-2026-109618 – PHP Group PHP (same weakness: CWE-416)
CVE-2026-109619 – PHP Group PHP (same weakness: CWE-416)
CVE-2026-69730 – Microsoft Windows (same weakness: CWE-416)

Browse all tracked CVEs in the defend.network CVE database →

🤖 This CVE page is generated by defend.network from NVD, CISA KEV, EPSS, and our verified daily briefings. Severity and exploitation data come from official sources; always verify remediation steps against the official vendor advisory before acting in production.