CVE intelligence and bounded remediation

CVE-2021-3733 — There's a flaw in urllib's AbstractBasicAuthHandler class

Medium CVSS 6.5

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.

Severity
Medium
CVSS
6.5 (3.1)
Published
2022-03-10
CISA KEV
Not currently listed
Ecosystem
python/pypi
Weaknesses
CWE-400

Affected products

  • python / python
  • 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

Showing 6 representative product identities from 27 source matches. Confirm exact affected versions with the linked vendor and NVD evidence.

Matched remediation archetype

Resource exhaustion and denial of service

This catalog composition supplies bounded fallback guidance. Explicitly reviewed curated workflows load with the complete record below.

Check exposure

  • Identify attacker-influenced work factors including input size, nesting, compression, fan-out, regex cost, allocation, recursion, retries, and connection lifetime.
  • Map per-request and shared CPU, memory, disk, descriptor, thread, queue, and downstream-service limits.
  • Determine whether authentication, tenancy, quotas, and rate controls apply before expensive processing begins.

Remediate safely

  • Bound input size, nesting, expansion, work, concurrency, queue depth, retries, and execution time before resource-intensive processing.
  • Release resources on every success, error, cancellation, and timeout path and use backpressure instead of unbounded buffering.
  • Update affected components and add small deterministic tests that assert resource ceilings rather than exhausting a host.

Authoritative sources

Complete CVE record and remediation plan

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