CVE-2026-3446: Python Software Foundation CPython · CWE-345
Affects Python Software Foundation CPythonSource CVE Database V5
Not known to be exploited · CVSS 6.0 Medium · fixed in 3.15.0a8 : update Python Software Foundation CPython when convenient.
Data as of 30 Oct 2026, 06:59 UTC
- EPSS
- 0.1% chance of exploitation in 30 days – higher than 8% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 3.15.0a8, 3.14.4, 3.13.13
CVSS:4.0/AV:N/AC:H/AT:P/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:NExploitation evidence
Disclosed: evidence found.
CVE published 10 Apr 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.
What to do
Upgrade Python Software Foundation CPython to 3.15.0a8, 3.14.4 or 3.13.13.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| Python Software FoundationCPython | Affected
| Fixed in
|
| Python Software FoundationCPython | Affected
| Fixed in
|
| Python Software FoundationCPython | Affected
| Fixed in
|
PyPIcpythonpkg:pypi/cpythonOther threats | Affected
| Fixed in– |
GitHubCPythonpkg:github/CPythonOther threats | Affected
| Fixed in
|
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
Users are advised to use the "validate=True" parameter in base64.b64decode() calls to enable stricter validation of base64 data, which mitigates the issue by rejecting improperly padded input.
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.
References
- github.com/python/cpython/pull/145267 (opens in a new tab)
- github.com/python/cpython/issues/145264 (opens in a new tab)
- mail.python.org/archives/list/security-announce@python.org/thread/F5ZT5ICGJ6CKXVUJ34YBVY7WOZ5SHG53/ (opens in a new tab)
- github.com/python/cpython/commit/1f9958f909c1b41a4ffc0b613ef8ec8fa5e7c474 (opens in a new tab)
- github.com/python/cpython/commit/4561f6418a691b3e89aef0901f53fe0dfb7f7c0e (opens in a new tab)
- github.com/python/cpython/commit/e31c55121620189a0d1a07b689762d8ca9c1b7fa (opens in a new tab)