CVE-2026-3446 MEDIUM

CVE-2026-3446: Base64 decoding stops at first padded quad by default

Vendor Python Software Foundation
Product CPython
Published April 10, 2026
Last update April 13, 2026

CVSS base score

6.0/10
Attack vector Network
Attack complexity High
Privileges required Low
User interaction None
Confidentiality
Integrity

CVSS vector

CVSS:4.0/AV:N/AC:H/AT:P/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N

What the vulnerability does

01Description

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.

Key dates

02Disclosure timeline

April 10, 2026 CVE published
April 13, 2026 Record updated