Vulnerability in Python Software Foundation Cpython

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…

EPSS: 0.000 (8.7th percentile) — read the EPSS interpretation.

Affected products

Python Software Foundation Cpython — versions 0, 3.14.0, 3.15.0a1

References

github.com/python/cpython/pull/145267 (patch)
github.com/python/cpython/issues/145264 (issue-tracking)
mail.python.org/archives/list/security-announce@python.org/thread/F5ZT5ICGJ6CKX… (vendor-advisory)
github.com/python/cpython/commit/1f9958f909c1b41a4ffc0b613ef8ec8fa5e7c474 (patch)
github.com/python/cpython/commit/4561f6418a691b3e89aef0901f53fe0dfb7f7c0e (patch)
github.com/python/cpython/commit/e31c55121620189a0d1a07b689762d8ca9c1b7fa (patch)