CVE-2026-3446: Python Software Foundation Cpython

Medium severity, CVSS 6.0. EPSS: 0.2% chance of exploitation in the next 30 days.

When calling base64.b64decode() or related functions the decoding process would stop after encountering the first padded quad regardless of whether there was more information to be processed. This can lead to data being accepted which may be processed differently by other implementations. Use "validate=True" to enable stricter processing of base64 data.

Affected products

• Python Software Foundation Cpython: before 3.13.13 (fixed in 3.13.13); from 3.14.0, before 3.14.4 (fixed in 3.14.4); from 3.15.0a1, before 3.15.0a8 (fixed in 3.15.0a8)

Published 2026-04-10. Last modified 2026-06-17.