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TI-2026-39910 Aliases CVE-2026-55233

OpenResty: Buffer overflow when writing PROXY protocol v2 header to upstream

Priority LOW 39CWE-787Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
Denial of service
Confidentiality · integrity · availability
None · None · High
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA. Impact type from CWE-787 and the CVSS impact.

Summary

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00488 42nd percentileScored 2026-11-07
Fix Fixed openresty (openresty): 1.29.2.5

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
Yes
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
openrestyopenresty1.29.2.1 to before 1.29.2.51.29.2.5Patch availableCNA
  • openresty Vendoropenresty Affected 1.29.2.1 to before 1.29.2.5 Fixed in 1.29.2.5 Patch available CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:openresty:openresty:*:*:*:*:*:*:*:*1.29.2.1 to before 1.29.2.5Vulnerableopenresty
  • cpe:2.3:a:openresty:openresty:*:*:*:*:*:*:*:* Versions 1.29.2.1 to before 1.29.2.5 Vulnerable ·openresty

Remediation

  • Fix · CNA openresty (openresty) Fixed in 1.29.2.5

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-55233

References

Patch 1

Advisory 1

  • TI-2023-23979 The HTTP/2 protocol allows a denial of service (server resource consumption) because… KEVCVSS 3.1HIGH 7.5
  • TI-2021-05876 A security issue in nginx resolver was identified, which might allow an attacker who is… CVSS 3.1HIGH 7.7
  • TI-2018-06684 In OpenResty through 1.13.6.1, URI parameters are obtained using the ngx.req.get_uri_args… CVSS 3.0CRITICAL 9.8
  • TI-2020-09415 An issue was discovered in OpenResty before 1.15.8.4. CVSS 3.1HIGH 7.5
  • TI-2024-26625 In lj_str_hash.c in OpenResty 1.19.3.1 through 1.25.3.1, the string hashing function… CVSS 3.1MEDIUM 5.9

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences