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Fencer Vulns
medium 6.0

CVE-2026-3446 json

Base64 decoding stops at first padded quad by default

published 2026-04-10 6 mo ago modified 2026-10-26 13 d ago also BIT-libpython-2026-3446 , BIT-python-2026-3446 , BIT-python-min-2026-3446 , EUVD-2026-21545

cvss
6.0
version 4.0, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 7%
public exploits
0
none known

Summary

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.

Patch / fix

  • bitnami libpython 3.13.13, 3.14.4
  • bitnami python 3.13.13, 3.14.4
  • bitnami python-min 3.13.13, 3.14.4
  • Python Software Foundation CPython 3.13.13, 3.14.4, 3.15.0a8
  • python3.13 Debian 13 3.13.5-2+deb13u2
  • python3.14 Debian 14 3.14.4-1

debian advisories DEBIAN-CVE-2026-3446

  • python3.11 hummingbird 1 3.11.16-1.1.hum1
  • python3.11-idle hummingbird 1 3.11.16-1.1.hum1
  • python3.11-libs hummingbird 1 3.11.16-1.1.hum1
  • python3.11-test hummingbird 1 3.11.16-1.1.hum1
  • python3.11-tkinter hummingbird 1 3.11.16-1.1.hum1
  • python3.12 hummingbird 1 3.12.14-1.hum1
  • python3.12-idle hummingbird 1 3.12.14-1.hum1
  • python3.12-libs hummingbird 1 3.12.14-1.hum1

red hat advisories RHSA-2026:60511RHSA-2026:58420RHSA-2026:10118RHSA-2026:7661RHSA-2026:7443

  • python3 SLES for SAP 15 SP6, SLES for SAP 15 SP5, SLES for SAP 15 SP4 +11 more 3.6.15-150300.10.129.1
  • python3-core SLES for SAP 15 SP6, SLES for SAP 15 SP5, SLES for SAP 15 SP4 +12 more 3.6.15-150300.10.129.1
  • grafana Multi Linux Manager Tools SLE-15 12.4.10-150002.4.27.1
  • mgr-push Multi Linux Manager Tools SLE-15 5.2.5-150002.3.12.1
  • spacecmd Multi Linux Manager Tools SLE-15 5.2.10-150002.3.15.1
  • uyuni-tools Multi Linux Manager Tools SLE-Micro-5, Multi Linux Manager Tools SLE-15 5.2.17-150002.3.20.1
  • venv-salt-minion Multi Linux Manager Tools SLE-Micro-5, Multi Linux Manager Tools SLE-15 3006.0-150002.5.22.1
  • spacewalk-client-tools Multi Linux Manager Tools SLE-15 5.2.7-150002.3.12.1

suse advisories SUSE-SU-2026:4754-1SUSE-SU-2026:4743-1SUSE-SU-2026:4585-1SUSE-SU-2026:4584-1SUSE-SU-2026:4583-1SUSE-SU-2026:4582-1

  • python3 openSUSE Leap 16.0 3.13.14-160000.1.1
  • python313 openSUSE Leap 16.0 3.13.14-160000.1.1
  • python313-core openSUSE Leap 16.0 3.13.14-160000.1.1
  • python313-nogil openSUSE Leap 16.0 3.13.14-160000.1.1
  • python313-documentation openSUSE Leap 16.0 3.13.14-160000.1.1
  • python313-nogil-nogil-core openSUSE Leap 16.0 3.13.14-160000.1.1
  • python314 openSUSE Tumbleweed 3.14.6-1.1
  • python312 openSUSE Tumbleweed 3.12.13-6.1

opensuse advisories openSUSE-SU-2026:21459-1openSUSE-SU-2026:11181-1openSUSE-SU-2026:11100-1openSUSE-SU-2026:11068-1openSUSE-SU-2026:10667-1openSUSE-SU-2026:10579-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-3446 updated cvss 5.3

python: Python base64: Incomplete data decoding due to premature stop at padding

  • Red Hat Enterprise Linux 9 python3.14, python3.14-idle, python3.14-libs, python3.14-test, python3.14-tkinter, python3.14-freethreading, +4 more Red Hat Enterprise Linux 10 python3.14
    affected: no fix available “Fix deferred”
  • Red Hat Hardened Images python3 3.14.4-1.hum1, python3.14 3.14.4-1.hum1, python3.12 3.12.14-1.hum1, python3.13 3.13.13-1.hum1, python3-idle 3.14.4-1.hum1, python3-libs 3.14.4-1.hum1, +27 more
    fixed: vendor fix RHSA-2026:7661
  • Red Hat Enterprise Linux 6 python, tkinter, python-libs, python-test, python-tools Red Hat Enterprise Linux 7 python, python3, tkinter, python-libs, python-test, python-tools, +4 more Red Hat Enterprise Linux 8 numpy, scipy, PyYAML, python3, mod_wsgi, python36, +89 more Red Hat Enterprise Linux 9 python3, python3.9, python3.11, python3.12, python3-idle, python3-libs, +11 more Red Hat Enterprise Linux 10 python3.12
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
6 mo ago

Exploit prediction

0.18% chance of exploitation in the next 30 days, higher than 7% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 4.0 6.0 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
CNA 4.0 6.0 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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Affected packages

ecosystem package affected fixed in
bitnami libpython
<3.13.13
>=3.14.0, <3.14.4
3.13.13
3.14.4
bitnami python
<3.13.13
>=3.14.0, <3.14.4
3.13.13
3.14.4
bitnami python-min
<3.13.13
>=3.14.0, <3.14.4
3.13.13
3.14.4

Affected products

  • Python Software Foundation CPython

Classification

Weakness
  • CWE-345 Insufficient Verification of Data Authenticity

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.