// For flags

CVE-2020-5236

Catastrophic backtracking in regex allows Denial of Service in Waitress

Severity Score

6.5
*CVSS v3.1

Exploit Likelihood

*EPSS

Affected Versions

*CPE

Public Exploits

1
*Multiple Sources

Exploited in Wild

-
*KEV

Decision

-
*SSVC
Descriptions

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.

Waitress versión 1.4.2, permite un ataque de DOS cuando waitress recibe un encabezado que contiene caracteres no válidos. Cuando un encabezado como "Bad-header: xxxxxxxxxxxxxxx\x10" es recibido, causará que el motor de expresión regular retroceda catastróficamente, provocando que el proceso utilice el 100% del tiempo de CPU y bloquee cualquier otras interacciones. Esto permite a un atacante enviar una única petición con un encabezado no válido y desconectar el servicio. Este problema fue introducido en la versión 1.4.2 cuando se actualizó la expresión regular para intentar hacer coincidir el comportamiento requerido por las erratas asociadas con RFC7230. La expresión regular que se usa para comprobar los encabezados entrantes se actualizó en la versión 1.4.3, se recomienda que las personas actualicen a la nueva versión de Waitress tan pronto como sea posible.

*Credits: N/A
CVSS Scores
Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High
Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
Required
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High
Attack Vector
Network
Attack Complexity
Low
Authentication
Single
Confidentiality
None
Integrity
None
Availability
Complete
* Common Vulnerability Scoring System
SSVC
  • Decision:-
Exploitation
-
Automatable
-
Tech. Impact
-
* Organization's Worst-case Scenario
Timeline
  • 2020-01-02 CVE Reserved
  • 2020-02-04 CVE Published
  • 2020-02-06 First Exploit
  • 2023-03-08 EPSS Updated
  • 2024-08-04 CVE Updated
  • ---------- Exploited in Wild
  • ---------- KEV Due Date
CWE
  • CWE-400: Uncontrolled Resource Consumption
CAPEC
Affected Vendors, Products, and Versions
Vendor Product Version Other Status
Vendor Product Version Other Status <-- --> Vendor Product Version Other Status
Agendaless
Search vendor "Agendaless"
 Waitress
Search vendor "Agendaless" for product "Waitress"
 1.4.2
Search vendor "Agendaless" for product "Waitress" and version "1.4.2"
-
Affected