Heap-based buffer overflow in NGINX ngx_http_proxy_v2_module and ngx_http_grpc_module
CVE-2026-42055 is a heap-based buffer overflow vulnerability in NGINX Open Source and NGINX Plus affecting the ngx_http_proxy_v2_module and ngx_http_grpc_module modules. The issue is reachable when NGINX is configured to proxy HTTP/2 traffic using proxy_http_version 2 or grpc_pass, while ignore_invalid_headers is set to off and large_client_header_buffers is configured larger than 2 MB. Under those conditions, a remote unauthenticated attacker can send oversized or malformed headers during upstream request creation, leading to memory corruption in the NGINX worker process. The immediate observable effect is worker process restart; under favorable exploit conditions, the memory corruption may be leveraged further for code execution.
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Impact, mitigation & remediation
What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.
Impact
What an attacker gets, and what they’ve been doing with it.
Mitigation
If you can’t patch tonight, do this now.
Remediation
Patch, then assume compromise.
Exploits
No public exploits tracked yet. Mallory keeps watching.
No public exploit code observed for this vulnerability.
Affected products & vendors
Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.
Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.
Recent activity
11 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A critical heap-based buffer overflow in NGINX Open Source and NGINX Plus HTTP proxy/gRPC modules that can be exploited remotely without authentication in non-default configurations, potentially causing denial of service or arbitrary code execution.
A high-risk vulnerability affecting NGINX proxy and gRPC modules that could be exploited to cause denial of service or execute malicious code under specific configurations.
A critical unauthenticated vulnerability in NGINX HTTP modules that can trigger a heap-based buffer overflow, causing worker process restart and potentially arbitrary code execution if ASLR is disabled or bypassed.
A critical NGINX vulnerability in ngx_http_proxy_v2_module and ngx_http_grpc_module that can be exploited by unauthenticated remote attackers to cause DoS or potentially achieve code execution on vulnerable systems with non-default configurations.
The version that knows your environment.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.