CVE-2026-55233: OpenResty: Buffer overflow when writing PROXY protocol v2 header to upstream
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.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
OpenRestyto a version that resolves this vulnerability.Fixed in 1.29.2.5 - Compensating control
If you have enabled sending PROXY protocol version 2 headers to upstream servers, disable PROXY protocol v2 for upstream connections until you can upgrade OpenResty to 1.29.2.5.
Event History
Frequently Asked Questions
What is the severity of CVE-2026-55233?
CVE-2026-55233 has a severity rating of 7.5, which is considered high.
How do I fix CVE-2026-55233?
To fix CVE-2026-55233, update OpenResty to version 1.29.2.5 or later.
What type of attack does CVE-2026-55233 expose systems to?
CVE-2026-55233 exposes systems to a buffer overflow attack that can potentially lead to service disruption.
What systems are affected by CVE-2026-55233?
CVE-2026-55233 affects OpenResty versions from 1.29.2.1 to prior to 1.29.2.5.
What is the impact of CVE-2026-55233 on confidentiality, integrity, and availability?
CVE-2026-55233 does not impact confidentiality or integrity, but it can affect availability due to potential service disruption.