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CVE-2026-55233— OpenResty: Buffer overflow when writing PROXY protocol v2 header to upstream

Quick assessment

Affected
openresty openresty
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

OpenResty是美国OpenResty组织开源的一款基于Nginx与Lua的Web应用服务器。 OpenResty 1.29.2.1版本至1.29.2.5之前版本存在缓冲区错误漏洞，该漏洞源于上游PROXY协议v2实现中存在越界写入，可能导致工作进程崩溃并造成拒绝服务。

CVSS 7.5 · High EPSS 0.49% · P42

Possible ATT&CK Techniques 1 AI

T1499 · Endpoint Denial of Service

Affected Version Matrix 1

VendorProduct Version RangeStatus
openresty openresty >= 1.29.2.1, < 1.29.2.5 affected
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I. Basic Information for CVE-2026-55233

Vulnerability Information
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Vulnerability Title
OpenResty: Buffer overflow when writing PROXY protocol v2 header to upstream
Source: CVE Program / CVE List V5
Vulnerability Description
OpenResty is a high performance web platform. From 1.29.2.1 to before 1.29.2.5, an out-of-bounds write vulnerability exists in the upstream PROXY protocol v2 implementation. When OpenResty is configured to send PROXY protocol version 2 headers to upstream servers, constructing the header in the stream proxy protocol v2 patch can write beyond the bounds of the allocated buffer, causing the worker process to crash and resulting in a denial of service. Only configurations that explicitly enable PROXY protocol v2 for upstream connections are impacted. This issue is fixed in version 1.29.2.5.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
跨界内存写
Source: CVE Program / CVE List V5
Vulnerability Title
OpenResty 缓冲区错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
OpenResty是美国OpenResty组织开源的一款基于Nginx与Lua的Web应用服务器。 OpenResty 1.29.2.1版本至1.29.2.5之前版本存在缓冲区错误漏洞，该漏洞源于上游PROXY协议v2实现中存在越界写入，可能导致工作进程崩溃并造成拒绝服务。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
openresty openresty >= 1.29.2.1, < 1.29.2.5 -

II. Public POCs for CVE-2026-55233

# POC Description Source Link Shenlong Link
AI-Generated POC Premium
Qwen3.6-35B-A3B · 7836 chars
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III. Intelligence Information for CVE-2026-55233

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Patches & Fixes for CVE-2026-55233 (1)

Vendor Advisories for CVE-2026-55233 (1)

IV. Related Vulnerabilities

Same vendor: openresty
Same weakness: CWE-787