// For flags

CVE-2021-21240

Regular Expression Denial of Service in httplib2

Severity Score

7.5
*CVSS v3.1

Exploit Likelihood

*EPSS

Affected Versions

*CPE

Public Exploits

1
*Multiple Sources

Exploited in Wild

-
*KEV

Decision

-
*SSVC
Descriptions

httplib2 is a comprehensive HTTP client library for Python. In httplib2 before version 0.19.0, a malicious server which responds with long series of "\xa0" characters in the "www-authenticate" header may cause Denial of Service (CPU burn while parsing header) of the httplib2 client accessing said server. This is fixed in version 0.19.0 which contains a new implementation of auth headers parsing using the pyparsing library.

httplib2 es una biblioteca cliente HTTP completa para Python. En httplib2 anterior a la versión 0.19.0, un servidor malicioso que responde con una larga serie de caracteres "\xa0" en el encabezado "www-authenticate" puede causar una Denegación de Servicio (CPU quemada mientras analiza el encabezado) del cliente httplib2 que accede a dicho servidor. Esto se corrigió en la versión 0.19.0, que contiene una nueva implementación de análisis de encabezados de autenticación usando la biblioteca pyparsing

An uncontrolled resource consumption flaw as found in python-httplib2, due to a flawed regular expression used while parsing the WWW-Authenticate header in an HTTP response. This flaw allows a malicious or compromised server to reply with a crafted sequence of characters in the WWW-Authenticate header, leading to a denial of service of the httplib2 client accessing the server. The highest threat from this vulnerability is to system availability.

*Credits: N/A
CVSS Scores
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High
Attack Vector
Network
Attack Complexity
Low
Authentication
None
Confidentiality
None
Integrity
None
Availability
Partial
* Common Vulnerability Scoring System
SSVC
  • Decision:-
Exploitation
-
Automatable
-
Tech. Impact
-
* Organization's Worst-case Scenario
Timeline
  • 2020-12-22 CVE Reserved
  • 2021-02-08 CVE Published
  • 2023-10-25 EPSS Updated
  • 2024-08-03 CVE Updated
  • 2024-08-03 First Exploit
  • ---------- 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
Httplib2 Project
Search vendor "Httplib2 Project"
 Httplib2
Search vendor "Httplib2 Project" for product "Httplib2"
 < 0.19.0
Search vendor "Httplib2 Project" for product "Httplib2" and version " < 0.19.0"
python
Affected