CVE-2026-55233Network attack vector

Worker-process crashes via unchecked PROXY v2 TLVs

Published Jul 10, 2026 · Updated Jul 10, 2026

Out-of-bounds write in OpenResty 1.29.2.1 through 1.29.2.4 allows remote attackers to crash worker processes via upstream traffic. The ngx_copy_tlv helper checks space for only a TLV header before copying its variable-length value, allowing that value to overrun the allocated header buffer. Only configurations explicitly selecting PROXY protocol v2 for upstream connections expose the fault; default v1 configurations are unaffected.

CVSS severity7.5
High
EPSS probability0.49%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds write in OpenResty 1.29.2.1 through 1.29.2.4 allows remote attackers to crash worker processes via upstream traffic. The ngx_copy_tlv helper checks space for only a TLV header before copying its variable-length value, allowing that value to overrun the allocated header buffer. Only configurations explicitly selecting PROXY protocol v2 for upstream connections expose the fault; default v1 configurations are unaffected.

The record

CVE
CVE-2026-55233
Published
Jul 10, 2026
Updated
Jul 10, 2026
Vendor
OpenResty Inc.
Product
OpenResty
Classifications
CWE-787, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 10, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 10, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>= 1.29.2.1, < 1.29.2.5

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

OpenResty Inc. · OpenRestyversion=>= 1.29.2.1, < 1.29.2.5

Published CVSS scores

7.5GitHubCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-787Out-of-bounds Write
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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