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CVE-2026-42055 is a heap-based buffer overflow vulnerability in NGINX Plus and NGINX Open Source affecting the ngx_http_proxy_v2_module and ngx_http_grpc_module modules. The flaw is triggered while NGINX constructs an upstream HTTP/2 request after accepting oversized client-supplied headers. Under a specific non-default configuration, NGINX does not correctly account for the full size of incoming headers when allocating memory for the upstream request, allowing a write past the end of a heap buffer in the worker process. Exploitation is possible by a remote, unauthenticated attacker who sends crafted large headers to a location that proxies HTTP/2 traffic using proxy_http_version 2 or gRPC traffic using grpc_pass, with ignore_invalid_headers disabled and large_client_header_buffers configured above 2 MB. The immediate result is memory corruption in the worker process, typically causing a crash and restart; in environments where ASLR is disabled or can be bypassed, the flaw may be leveraged for arbitrary code execution.
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No valid public exploits. Mallory filtered out 2 candidates as fakes, detection scripts, or README-only repos.
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62 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A heap buffer overflow in NGINX mentioned only in passing as another XGPT discovery; no further technical or exploitation details are provided in this content.
Another vulnerability referenced only as background; its fixes do not remediate CVE-2026-42533.
Another nginx vulnerability mentioned only as background; fixes for it do not address CVE-2026-42533.
Another CVE mentioned only for comparison; its fixes do not address CVE-2026-42533.
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.
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Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.