CVE-2021-3733

MEDIUM
6.5
CVSS Score
Published: March 7, 2022 at 12:00 AM UTC
Updated: October 14, 2026 at 10:17 AM UTC
20 products affected across 4 vendorsFedoraEnterprise LinuxEnterprise Linux Server Aus

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Severity
MEDIUM6.5
Exploit prediction
EPSS 5%
SSVC
No known exploit

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.

Affected

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

v < 3.6.143.7.0 ≤ v < 3.7.113.8.0 ≤ v < 3.8.103.9.0 ≤ v < 3.9.53.10.0
Vendor states this is fixed in 3.6.14 (unaffected)
Affected range stops below 3.7.11, so it looks safe — our inference, not a vendor statement
Affected range stops below 3.8.10, so it looks safe — our inference, not a vendor statement
Affected range stops below 3.9.5, 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:

SSVC — Action Prioritization

SSVCNo known exploitAutomatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

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

Quick Info

StatusMODIFIED
CWE
CWE-400

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