Disclosure summary
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.
Source-reported weakness categories
CWE-400
Source-specific records & product guidance
Sources retain their own attribution and scoring. Follow the original record to confirm affected versions, fixed releases, and configuration conditions.
NIST National Vulnerability Database · NVD-CVE-2021-3733
Open original source · Updated Oct 08, 2026
Only CPE matches marked vulnerable=true are indexed. AND/OR platform conditions must be checked in the original NVD record.
| Vendor | Product / association | Version / bounds |
|---|---|---|
| python | python | * {"versionStartIncluding":"3.9.0","versionEndExcluding":"3.9.5"} |
| python | python | 3.10.0 |
| redhat | codeready_linux_builder | 8.0 |
| redhat | codeready_linux_builder_for_ibm_z_systems | 8.0 |
| redhat | codeready_linux_builder_for_power_little_endian | 8.0 |
| redhat | enterprise_linux | 8.0 |
| redhat | enterprise_linux_eus | 8.4 |
| redhat | enterprise_linux_for_ibm_z_systems | 8.0 |
| redhat | enterprise_linux_for_ibm_z_systems_eus | 8.4 |
| redhat | enterprise_linux_for_power_little_endian | 8.0 |
| redhat | enterprise_linux_for_power_little_endian_eus | 8.4 |
| redhat | enterprise_linux_server_aus | 8.4 |
| redhat | enterprise_linux_server_for_power_little_endian_update_services_for_sap_solutions | 8.4 |
| redhat | enterprise_linux_server_tus | 8.4 |
| redhat | enterprise_linux_server_update_services_for_sap_solutions | 8.4 |
| fedoraproject | extra_packages_for_enterprise_linux | 7.0 |
| fedoraproject | fedora | 33 |
| fedoraproject | fedora | 34 |
| fedoraproject | fedora | 35 |
| fedoraproject | fedora | 36 |
| netapp | management_services_for_element_software_and_netapp_hci | - |
| netapp | ontap_select_deploy_administration_utility | - |
| netapp | solidfire,_enterprise_sds_&_hci_storage_node | - |
| netapp | hci_compute_node_firmware | - |
Original records & references
- NIST NVD record
- CVE Program record
- bugs.python.org — Exploit, Issue Tracking, Patch, Vendor Advisory
- bugzilla.redhat.com — Issue Tracking, Third Party Advisory
- github.com — Patch, Third Party Advisory
- github.com — Patch, Third Party Advisory
- lists.debian.org
- lists.debian.org
- security.netapp.com — Third Party Advisory
- ubuntu.com — Patch, Third Party Advisory
- bugs.python.org — Exploit, Issue Tracking, Patch, Vendor Advisory
- bugzilla.redhat.com — Issue Tracking, Third Party Advisory
- github.com — Patch, Third Party Advisory
- github.com — Patch, Third Party Advisory
- lists.debian.org
- lists.debian.org
- lists.debian.org
- security.netapp.com — Third Party Advisory
- ubuntu.com — Patch, Third Party Advisory
PUBLISHED 2022-03-10T12:42:59-05:00
MODIFIED 2026-10-08T17:17:41-04:00
INGESTED 2026-10-10T20:50:21-04:00