CVE-2026-55233

Received Received - Intake

Out-of-Bounds Write in OpenResty PROXY Protocol v2

Publication date: 2026-07-10

Last updated on: 2026-07-10

Assigner: GitHub, Inc.

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.

CVSS Scores

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Meta Information

Published

2026-07-10

Last Modified

2026-07-10

Generated

2026-07-11

AI Q&A

2026-07-11

EPSS Evaluated

N/A

NVD

CVE-2026-55233

Affected Vendors & Products

Vendor	Product	Version / Range
openresty	openresty	to 1.29.2.5 (exc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-787	The product writes data past the end, or before the beginning, of the intended buffer.

Attack-Flow Graph

Executive Summary

This vulnerability exists in OpenResty versions from 1.29.2.1 to before 1.29.2.5 in the implementation of the upstream PROXY protocol version 2. When OpenResty is configured to send PROXY protocol v2 headers to upstream servers, the construction of these headers can cause an out-of-bounds write beyond the allocated buffer. This means that the software writes data outside the memory area it should, which can cause the worker process to crash.

Only configurations that explicitly enable PROXY protocol v2 for upstream connections are affected by this issue. The vulnerability is fixed in OpenResty version 1.29.2.5.

Impact Analysis

The primary impact of this vulnerability is a denial of service (DoS). Because the out-of-bounds write can cause the worker process to crash, the affected OpenResty server may become unavailable or unstable, disrupting service availability.

Mitigation Strategies

To mitigate this vulnerability, upgrade OpenResty to version 1.29.2.5 or later, where the issue is fixed.

Additionally, review your OpenResty configuration and disable the use of PROXY protocol version 2 for upstream connections if it is not explicitly required.

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