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Description

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.

PUBLISHED Reserved 2026-03-02 | Published 2026-04-10 | Updated 2026-04-13 | Assigner PSF




MEDIUM: 6.0CVSS:4.0/AV:N/AC:H/AT:P/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N

Product status

Default status
unaffected

Any version before 3.13.13
affected

3.14.0 (python) before 3.14.4
affected

3.15.0a1 (python) before 3.15.0a8
affected

Credits

Serhiy Storchaka reporter

References

github.com/python/cpython/pull/145267 patch

github.com/python/cpython/issues/145264 issue-tracking

mail.python.org/.../thread/F5ZT5ICGJ6CKXVUJ34YBVY7WOZ5SHG53/ vendor-advisory

github.com/...ommit/1f9958f909c1b41a4ffc0b613ef8ec8fa5e7c474 patch

github.com/...ommit/4561f6418a691b3e89aef0901f53fe0dfb7f7c0e patch

github.com/...ommit/e31c55121620189a0d1a07b689762d8ca9c1b7fa patch

cve.org (CVE-2026-3446)

nvd.nist.gov (CVE-2026-3446)

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