CVE-2020-36661

Denial of service via unbounded header regex

Published Feb 12, 2023 · Updated Mar 24, 2025

Regular expression denial of service in Kong Inc. lua-multipart 0.5.8-1 allows attackers to hang multipart parsing with long header input. The is_header function applies the unanchored (%S+):%s*(%S+) pattern to each candidate header even though its captures are unused, causing rejection time to grow drastically on long nonmatching strings. Reachability depends on a consuming application passing attacker-controlled multipart header lines to the parser; excessive CPU use can stall its request processing.

CVSS severity7.5
High
EPSS probability0.92%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Regular expression denial of service in Kong Inc. lua-multipart 0.5.8-1 allows attackers to hang multipart parsing with long header input. The is_header function applies the unanchored (%S+):%s*(%S+) pattern to each candidate header even though its captures are unused, causing rejection time to grow drastically on long nonmatching strings. Reachability depends on a consuming application passing attacker-controlled multipart header lines to the parser; excessive CPU use can stall its request processing.

The record

CVE
CVE-2020-36661
Published
Feb 12, 2023
Updated
Mar 24, 2025
Vendor
Kong Inc.
Product
lua-multipart
Classifications
CWE-1333, T1499.004
Attack vector
Unavailable
Privileges
Unavailable

Timeline

How it unfolded

  1. Feb 12, 2023CVE publishedPublication date reported by the CVE source.
  2. Mar 24, 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?

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

  1. Affected versionversion=0.5.8-1

What conditions does exploitation require?

Attack vectorUnavailable in this record.
Required privilegesUnavailable in this record.

What is affected?

Kong Inc. · lua-multipartversion=0.5.8-1

Published CVSS scores

7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
2.7VulDBAV:A/AC:L/Au:S/C:N/I:N/A:P
3.5VulDBCVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L

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)
VectorUnavailable
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-1333Inefficient Regular Expression Complexity
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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