CVE-2026-3446

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.

Score

CVSS 4.0 6.0 Medium

Status

Awaiting Analysis - cna@python.org

Published

2026-04-10

Last modified

2026-10-26

Weaknesses

CWE-345

Affected products

• Cpython (Python Software Foundation)

References

• https://github.com/python/cpython/pull/145267
• https://github.com/python/cpython/issues/145264
• https://mail.python.org/archives/list/security-announce@python.org/thread/F5ZT5ICGJ6CKXVUJ34YBVY7WOZ5SHG53/
• https://github.com/python/cpython/commit/1f9958f909c1b41a4ffc0b613ef8ec8fa5e7c474
• https://github.com/python/cpython/commit/4561f6418a691b3e89aef0901f53fe0dfb7f7c0e
• https://github.com/python/cpython/commit/e31c55121620189a0d1a07b689762d8ca9c1b7fa