CVE-2026-3446Base64 decoding stops at first padded quad by default
Updated under an hour ago ()
Does this affect you?
It affects Python Software Foundation CPython. Add what you run to find out whether that includes you.
No exploitation reported and no EPSS estimate yet.
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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.
- CVSS
- 6.0 MEDIUM (v4.0, CNA)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
- Weakness (CWE)
- CWE-345
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- PSF
- NVD analysis
- Awaiting Analysis
- Record last updated
- Apr 13, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
Python Software Foundation CPython python_software_foundation:cpython (from the name) | before 3.13.13; from 3.14.0 before 3.14.4; from 3.15.0a1 before 3.15.0a8 | CNA record |
References
- https://github.com/python/cpython/pull/145267patch
- https://github.com/python/cpython/issues/145264issue-tracking
- https://mail.python.org/archives/list/security-announce@python.org/thread/F5ZT5ICGJ6CKXVUJ34YBVY7WOZ5SHG53/vendor-advisory
- https://github.com/python/cpython/commit/1f9958f909c1b41a4ffc0b613ef8ec8fa5e7c474patch
- https://github.com/python/cpython/commit/4561f6418a691b3e89aef0901f53fe0dfb7f7c0epatch
- https://github.com/python/cpython/commit/e31c55121620189a0d1a07b689762d8ca9c1b7fapatch
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.