CVE-2026-42055

What it is

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.

At a glance

Exploitability

Can be exploited over the network without logging in. High risk of data exposure, data tampering, service disruption.

Exploit odds

6.5% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2026-06-17 15:16 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-09-14 13:18 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 6.5% in the next 30 days (EPSS).
• Severity: 9.2 CRITICAL (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2026-06-17 15:16 UTC

Last modified

2026-09-14 13:18 UTC

Exploit probability

6.5% · EPSS, next 30 days

Weakness

CWE-122

Record status

Modified

Affected

• f5 Dos ≤ 4.7.0
• f5 Dos 4.9.0
• f5 nginx Gateway Fabric ≤ 1.6.2
• f5 nginx Gateway Fabric ≤ 2.6.3
• f5 nginx Ingress Controller ≤ 3.7.2
• f5 nginx Ingress Controller ≤ 4.0.1
• f5 nginx Ingress Controller ≤ 5.5.0
• f5 nginx Instance Manager ≤ 2.22.0

Attack profile CVSS 4.0 · 9.2

Attack vector

Network

Complexity

High

Attack requirements

Present

Privileges needed

None

User interaction

None

Confidentiality

High

Integrity

High

Availability

High

Is it in your code?

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