Vulnary
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Critical· 9.2

CVE-2026-42055

NGINX Plus and NGINX Open Source can crash or allow code execution when proxying HTTP/2 traffic with large headers. The flaw occurs when the proxy_http_version or grpc_pass directives are used together with ignore_invalid_headers set to off and large_client_header_buffers larger than 2 MB, causing a heap‑based buffer overflow. The vulnerability is rated critical.

publishedJun 17, 2026
last modifiedJul 28, 2026
sourcesNVD
severity · cvss
9.2
critical · how bad it is
exploitation · epss
4%
90th percentile · chance of exploitation in 30 days
(ai-assisted) A model wrote this summary from the official data, so double-check it against the source before you act on it. Read the official advisory →
auto-deletes from the system
counting…on Sep 7, 2026

No official fix yet. If none appears within 45 days of first tracking, this entry is removed automatically.

01

Who is affected

NGINX Plus and NGINX Open Source, including F5 NGiNX products such as nginx_app_protect_dos, nginx_app_protect_waf, nginx_gateway_fabric, nginx_ingress_controller (4.0.0, 4.0.1), nginx_instance_manager, nginx_open_source (1.31.1), nginx_plus, nginx_plus r3, and nginx_plus r30.

02

Real-world impact

An attacker can send oversized HTTP/2 headers to trigger a heap overflow, causing the worker process to crash or, if ASLR is disabled, to execute arbitrary code on the server.

03

Why this severity

The CVSS score of 9.2 reflects a critical vulnerability: it is remote, unauthenticated, requires no user interaction, and can lead to code execution or denial of service with high impact.

04

What to do about it

no official fix yet

No official fix or mitigation is documented in the sources yet. Monitor the vendor advisory and apply the patch as soon as it is released.

No fix documented in sources

05

Timeline

  1. Jun 17, 2026 · Jun 17, 2026
    Published
    Disclosed and added to the National Vulnerability Database.
  2. Jul 28, 2026 · 7d ago
    Advisory updated
    The NVD record was last revised.
06

How it’s attacked

Attack vectorNetwork (remote)
Attack complexityHigh
Attack requirementsPresent
Privileges requiredNone
User interactionNone needed
Confidentiality impactHigh
Integrity impactHigh
Availability impactHigh
07

References & advisories

NVD advisory ↗Search advisories ↗
(ai-assisted) A model wrote this summary from the official data, so double-check it against the source before you act on it. Read the official advisory →