An issue was discovered in Python before 3.11.1.

Summary

An issue was discovered in Python before 3.11.1. An unnecessary quadratic algorithm exists in one path when processing some inputs to the IDNA (RFC 3490) decoder, such that a crafted, unreasonably long name being presented to the decoder could lead to a CPU denial of service. Hostnames are often supplied by remote servers that could be controlled by a malicious actor; in such a scenario, they could trigger excessive CPU consumption on the client attempting to make use of an attacker-supplied supposed hostname. For example, the attack payload could be placed in the Location header of an HTTP response with status code 302. A fix is planned in 3.11.1, 3.10.9, 3.9.16, 3.8.16, and 3.7.16.

Timeline

1. Nov 9, 2022, 12:00 AM UTCCVE published
2. May 1, 2025, 2:24 PM UTCCISA SSVC assessment

   Exploitation: poc · Automatable: yes · Technical impact: partial

3. Oct 14, 2026, 6:35 PM UTCRecord last updated

Affected versions

• libpythonBitnami

  fixed in 3.7.16; From 3.10.0 · fixed in 3.10.9; From 3.11.0 · fixed in 3.11.1; From 3.8.0 · fixed in 3.8.16; From 3.9.0 · fixed in 3.9.16

• pythonBitnami

  fixed in 3.7.16; From 3.10.0 · fixed in 3.10.9; From 3.11.0 · fixed in 3.11.1; From 3.8.0 · fixed in 3.8.16; From 3.9.0 · fixed in 3.9.16

• python-minBitnami

  fixed in 3.7.16; From 3.10.0 · fixed in 3.10.9; From 3.11.0 · fixed in 3.11.1; From 3.8.0 · fixed in 3.8.16; From 3.9.0 · fixed in 3.9.16

References 25