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CVE-2020-5236— Catastrophic backtracking in regex allows Denial of Service in Waitress

Quick assessment

Affected
Pylons Waitress
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Waitress是一款用于Python的WSGI（Web服务器网关接口）服务器。 Agendaless Waitress 1.4.2版本中存在资源管理错误漏洞。该漏洞源于网络系统或产品对系统资源（如内存、磁盘空间、文件等）的管理不当。

CVSS 5.7 · Medium EPSS 2.36% · P83

Possible ATT&CK Techniques 1 AI

T1499 · Endpoint Denial of Service
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I. Basic Information for CVE-2020-5236

Vulnerability Information
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Vulnerability Title
Catastrophic backtracking in regex allows Denial of Service in Waitress
Source: CVE Program / CVE List V5
Vulnerability Description
Waitress version 1.4.2 allows a DOS attack When waitress receives a header that contains invalid characters. When a header like "Bad-header: xxxxxxxxxxxxxxx\x10" is received, it will cause the regular expression engine to catastrophically backtrack causing the process to use 100% CPU time and blocking any other interactions. This allows an attacker to send a single request with an invalid header and take the service offline. This issue was introduced in version 1.4.2 when the regular expression was updated to attempt to match the behaviour required by errata associated with RFC7230. The regular expression that is used to validate incoming headers has been updated in version 1.4.3, it is recommended that people upgrade to the new version of Waitress as soon as possible.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
未加控制的资源消耗(资源穷尽)
Source: CVE Program / CVE List V5
Vulnerability Title
Agendaless Waitress 资源管理错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Waitress是一款用于Python的WSGI（Web服务器网关接口）服务器。 Agendaless Waitress 1.4.2版本中存在资源管理错误漏洞。该漏洞源于网络系统或产品对系统资源（如内存、磁盘空间、文件等）的管理不当。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Pylons Waitress = 1.4.2 -

II. Public POCs for CVE-2020-5236

# POC Description Source Link Shenlong Link
1 Waitress 1.4.2 ReDoS - CVE-2020-5236 (Blog Sample Code) https://github.com/motikan2010/CVE-2020-5236 POC Details
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III. Intelligence Information for CVE-2020-5236

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Patches & Fixes for CVE-2020-5236 (1)

Vendor Advisories for CVE-2020-5236 (1)

IV. Related Vulnerabilities

Same product: Waitress
Same vendor: Pylons
Same weakness: CWE-400

V. Comments for CVE-2020-5236

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