CVE-2021-3733

Description

There's a flaw in urllib's AbstractBasicAuthHandler class. An attacker who controls a malicious HTTP server that an HTTP client (such as web browser) connects to, could trigger a Regular Expression Denial of Service (ReDOS) during an authentication request with a specially crafted payload that is sent by the server to the client. The greatest threat that this flaw poses is to application availability.

How to fix CVE-2021-3733

To remediate CVE-2021-3733, upgrade the affected package to a fixed version below.

—upgrade to 3.6.14 or later
—upgrade to 3.6.14 or later
—upgrade to 3.6.14 or later
—upgrade to 7.3.5+dfsg-2 or later
—no fix listed
—upgrade to 3.5.3-1+deb9u5 or later
—upgrade to 3.9.2-1+deb11u2 or later

Is CVE-2021-3733 being exploited?

Low — EPSS is 0.6%, meaning exploitation activity has not been observed at scale.

Affected packages (7)

from 0, < 3.6.14, >= 3.7.0, < 3.7.11, >= 3.8.0, < 3.8.10, >= 3.9.0, < 3.9.5
from 0, < 3.6.14, >= 3.7.0, < 3.7.11, >= 3.8.0, < 3.8.10, >= 3.9.0, < 3.9.5
from 0, < 3.6.14, >= 3.7.0, < 3.7.11, >= 3.8.0, < 3.8.10, >= 3.9.0, < 3.9.5, >= 3.10.0, < 3.10.1
from 0, < 7.3.5+dfsg-2
from 0
from 0, < 3.5.3-1+deb9u5
from 0, < 3.9.2-1+deb11u2

CVSS scores

Source	Version	Severity	Vector
osv	CVSS 3.1	MEDIUM6.5	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H