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CVE-2026-42055 represents a severe memory corruption vulnerability located within the upstream proxy modules of NGINX, specifically impacting `ngx_http_proxy_v2_module` and ngx_http_grpc_module.
When an enterprise deployment configures NGINX to handle HTTP/2 traffic forwarding or gRPC backend proxying with specific custom parameters, proper input size validation fails.
Specifically, when handling incoming HTTP/2 requests featuring extremely large or meticulously crafted header fields alongside expanded buffer allocations, incorrect buffer calculations occur.
An unauthenticated remote attacker can exploit this architectural flaw by transmitting specially structured header payloads across established HTTP/2 network channels.
Upon receipt, the parsing engine allocates inadequate memory buffers or miscalculates bounds during the decoding process, leading directly to a heap-based buffer overflow.
This out-of-bounds write condition corrupts adjacent heap memory structures within the worker process execution space.
As an immediate consequence, the affected NGINX worker process encounters a fatal exception, triggering an automatic panic and restart cycle.
In production environments handling high-concurrency traffic streams, repeated exploitation induces a persistent and effective Denial of Service condition.
Beyond standard service interruption symptoms, advanced exploit vectors can potentially achieve arbitrary code execution under specific low-privilege boundary conditions.
Particularly on systems where Address Space Layout Randomization is absent, disabled, or successfully bypassed via information disclosure gadgets, control flow hijacking becomes feasible.
The vulnerability highlights the inherent risks associated with non-default buffer directives such as oversized client header configurations combined with disabled header validation checks.
Mitigation requires immediate application of official security updates, dropping vulnerable fork versions, or enforcing strict boundary configurations across all cluster ingress controllers.
Upgrading ingress-nginx implementations to version `v1.30.5` ensures the underlying NGINX engine incorporates the necessary upstream patches to fully neutralize this vector.
DailyCVE Form:
Platform: NGINX Kubernetes
Version: v1.30.5
Vulnerability: Heap Overflow
Severity: Important
date: July 2026
Prediction: Patched Now
What Undercode Say:
Using Helm to upgrade ingress-nginx to secure release
helm upgrade ingress-nginx ingress-nginx/ingress-nginx
–set controller.image.tag=v1.30.5
Using kubectl to apply secure manifests
kubectl apply -f https://raw.githubusercontent.com/baranchen/ingress-nginx/main/deploy/static/provider/cloud/deploy.yaml
Verify NGINX version inside running controller pod
kubectl exec -it deployment/ingress-nginx-controller — nginx -v
Exploit: (Educational Purposes!)
Conceptual validation script outline for HTTP/2 header buffer testing
import h2.connection
import h2.config
import socket
def test_overflow():
Establish socket connection to target NGINX ingress node
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect((“target_ingress_ip”, 443))
Send crafted large HTTP/2 headers via gRPC/HTTP2 proxy path
Triggers incorrect buffer calculation in ngx_http_proxy_v2_module
s.close()
Protection: from this CVE
Upgrade the NGINX core engine to version 1.30.3 or newer, or deploy ingress-nginx community fork version v1.30.5 which includes upstream security backports.
Ensure configuration directives like `ignore_invalid_headers` remain enabled and avoid setting `large_client_header_buffers` above 2 megabytes.
Restrict external proxy paths where HTTP/2 or gRPC upstream proxying is unverified or unnecessary.
Impact:
Remote unauthenticated attackers can cause persistent Denial of Service via NGINX worker crashes.
Potential for arbitrary code execution if memory protection mechanisms like ASLR are bypassed or disabled.
Compromise of cluster ingress availability and application gateway stability across multi-tenant Kubernetes environments.
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Sources:
Reported By: github.com
Extra Source Hub:
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