CVE-2026-3446
Base64 decoding stops at first padded quad by default
CVSS Score
0.0
EPSS Score
0.1%
EPSS Percentile
15th
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.
| Vendor | python software foundation |
| Product | cpython |
| Published | Apr 10, 2026 |
| Last Updated | Apr 13, 2026 |
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Affected Versions
Python Software Foundation / CPython
0 < 3.13.13 3.14.0 < 3.14.4 3.15.0a1 < 3.15.0a8
References
github.com: https://github.com/python/cpython/pull/145267 github.com: https://github.com/python/cpython/issues/145264 mail.python.org: https://mail.python.org/archives/list/[email protected]/thread/F5ZT5ICGJ6CKXVUJ34YBVY7WOZ5SHG53/ github.com: https://github.com/python/cpython/commit/1f9958f909c1b41a4ffc0b613ef8ec8fa5e7c474 github.com: https://github.com/python/cpython/commit/4561f6418a691b3e89aef0901f53fe0dfb7f7c0e github.com: https://github.com/python/cpython/commit/e31c55121620189a0d1a07b689762d8ca9c1b7fa
Credits
🔍 Serhiy Storchaka