CVE-2021-21240

Regular Expression Denial of Service in httplib2

HIGH
7.5
CVSS Score
Published: February 8, 2021 at 07:45 PM UTC
Updated: June 17, 2026 at 03:35 AM UTC
1 product affected across 1 vendorHTTPLIB2

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Severity
HIGH7.5
Exploit prediction
EPSS 4%

Description

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

v < 0.19.0
Affected range stops below 0.19.0, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

References (4)

x_refsource_MISCPatchThird Party Advisory
https://github.com/httplib2/httplib2/pull/182
x_refsource_CONFIRMExploitMitigationThird Party Advisory
https://github.com/httplib2/httplib2/security/advisories/GHSA-93xj-8mrv-444m
x_refsource_MISCProductThird Party Advisory
https://pypi.org/project/httplib2

CVSS

7.5HIGHGitHub_M
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
NONE
Availability
HIGH
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-400

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