CVE-2020-36309Network attack vector

HTTP header injection via unchecked control characters

Published Apr 6, 2021 · Updated Nov 3, 2025

Input validation in OpenResty lua-nginx-module before 0.10.16 allows remote attackers to inject HTTP headers via control characters. The ngx.req.set_uri, ngx.req.set_header, ngx.header, and ngx.redirect paths accept unsafe bytes and truncate CR or LF instead of rejecting the input. Reachability requires Lua application logic to pass attacker-controlled strings into an affected mutation API, enabling alteration of request or response metadata.

CVSS severity5.3
Medium
EPSS probability1.42%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Input validation in OpenResty lua-nginx-module before 0.10.16 allows remote attackers to inject HTTP headers via control characters. The ngx.req.set_uri, ngx.req.set_header, ngx.header, and ngx.redirect paths accept unsafe bytes and truncate CR or LF instead of rejecting the input. Reachability requires Lua application logic to pass attacker-controlled strings into an affected mutation API, enabling alteration of request or response metadata.

The record

CVE
CVE-2020-36309
Published
Apr 6, 2021
Updated
Nov 3, 2025
Vendor
Unknown vendor
Product
Unknown product
Classifications
T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 6, 2021CVE publishedPublication date reported by the CVE source.
  2. Nov 3, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

5.3NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:P/A:N

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.

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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

T1190Exploit Public-Facing Application

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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