Vulnerability Database

357,869

Total vulnerabilities in the database

CVE-2026-42055 — f5 / dos

Heap-based Buffer Overflow

NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_proxy_v2_module and ngx_http_grpc_module modules. This vulnerability exists when the proxy_http_version to 2 or grpc_pass directives are used to proxy HTTP/2 traffic, the ignore_invalid_headers directive is set to off, and the large_client_header_buffers directive size is larger than 2 megabytes. A remote, unauthenticated attacker, along with conditions beyond their control, could send large headers while creating an upstream request. This may cause a heap-based buffer overflow 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.

  • Published: Jun 17, 2026
  • Updated: Jun 20, 2026
  • CVE: CVE-2026-42055
  • Severity: Critical
  • Exploit:
  • CISA KEV:

CVSS v3:

  • Severity: High
  • Score: 8.1
  • AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Software From Fixed in
f5 / dos 4.9.0 4.9.0.x
f5 / nginx_app_protect_dos 4.3.0 4.7.0.x
f5 / nginx_app_protect_waf 4.10.0 4.16.0.x
f5 / nginx_app_protect_waf 5.2.0 5.8.0.x
f5 / nginx_gateway_fabric 1.3.0 1.6.2.x
f5 / nginx_gateway_fabric 2.0.0 2.6.4
f5 / nginx_ingress_controller 3.5.0 3.7.2.x
f5 / nginx_ingress_controller 5.0.0 5.5.1
f5 / nginx_ingress_controller 4.0.0 4.0.0.x
f5 / nginx_ingress_controller 4.0.1 4.0.1.x
f5 / nginx_instance_manager 2.17.0 2.22.0.x
f5 / nginx_open_source 1.30.0 1.30.3
f5 / nginx_open_source 1.31.1 1.31.1.x
f5 / nginx_plus 37.0.0 37.0.1.x
f5 / nginx_plus r3 r3.x
f5 / nginx_plus r30 r30.x
f5 / nginx_plus r30-p1 r30-p1.x
f5 / nginx_plus r30-p2 r30-p2.x
f5 / nginx_plus r31 r31.x
f5 / nginx_plus r31-p1 r31-p1.x
f5 / nginx_plus r31-p2 r31-p2.x
f5 / nginx_plus r31-p3 r31-p3.x
f5 / nginx_plus r32 r32.x
f5 / nginx_plus r32-p1 r32-p1.x
f5 / nginx_plus r32-p2 r32-p2.x
f5 / nginx_plus r32-p3 r32-p3.x
f5 / nginx_plus r32-p4 r32-p4.x
f5 / nginx_plus r33 r33.x
f5 / nginx_plus r33-p1 r33-p1.x
f5 / nginx_plus r33-p2 r33-p2.x
f5 / nginx_plus r33-p3 r33-p3.x
f5 / nginx_plus r34 r34.x
f5 / nginx_plus r34-p1 r34-p1.x
f5 / nginx_plus r34-p2 r34-p2.x
f5 / nginx_plus r35 r35.x
f5 / nginx_plus r35-p1 r35-p1.x
f5 / nginx_plus r36 r36.x
f5 / nginx_plus r36-p1 r36-p1.x
f5 / nginx_plus r36-p2 r36-p2.x
f5 / nginx_plus r36-p3 r36-p3.x
f5 / nginx_plus r36-p4 r36-p4.x
f5 / nginx_plus r36-p5 r36-p5.x
f5 / waf 5.9.0 5.13.1.x
f5 / waf 4.8.1 4.8.1.x

Frequently Asked Questions

A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.

CVSS (Common Vulnerability Scoring System) estimates technical severity, but it doesn't automatically equal business risk. Prioritize using context like internet exposure, affected asset criticality, known exploitation (proof-of-concept or in-the-wild), and whether compensating controls exist. A "Medium" CVSS on an exposed, production system can be more urgent than a "Critical" on an isolated, non-production host.

A vulnerability is the underlying weakness. An exploit is the method or code used to take advantage of it. A zero-day is a vulnerability that is unknown to the vendor or has no publicly available fix when attackers begin using it. In practice, risk increases sharply when exploitation becomes reliable or widespread.

Recurring findings usually come from incomplete Asset Discovery, inconsistent patch management, inherited images, and configuration drift. In modern environments, you also need to watch the software supply chain: dependencies, containers, build pipelines, and third-party services can reintroduce the same weakness even after you patch a single host. Unknown or unmanaged assets (often called Shadow IT) are a common reason the same issues resurface.

Use a simple, repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress using consistent metrics so remediation is steady, not reactive.

SynScan combines attack surface monitoring and continuous security auditing to keep your inventory current, flag high-impact vulnerabilities early, and help you turn raw findings into a practical remediation plan.