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Fencer Vulns
medium 5.7

CVE-2021-3426 json

There's a flaw in Python 3's pydoc.

published 2021-05-20 5 y ago modified 2026-10-14 26 d ago also BIT-libpython-2021-3426 , BIT-python-2021-3426 , BIT-python-min-2021-3426 , EUVD-2021-26753

cvss
5.7
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
1.9%
EPSS 1.9% chance of exploitation in 30 days, percentile 79%
public exploits
0
none known

Summary

There's a flaw in Python 3's pydoc. A local or adjacent attacker who discovers or is able to convince another local or adjacent user to start a pydoc server could access the server and use it to disclose sensitive information belonging to the other user that they would not normally be able to access. The highest risk of this flaw is to data confidentiality. This flaw affects Python versions before 3.8.9, Python versions before 3.9.3 and Python versions before 3.10.0a7.

Patch / fix

  • bitnami libpython 2.7.18, 3.6.13, 3.7.10, 3.8.8, 3.9.3
  • bitnami python 2.7.18, 3.6.13, 3.7.10, 3.8.8, 3.9.3
  • bitnami python-min 2.7.18, 3.6.13, 3.7.10, 3.8.8, 3.9.3
  • Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP V3.1.5
  • Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP V3.1.5
  • Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP V3.1.5
  • pypy3 Debian 14, Debian 13, Debian 12 7.3.3+dfsg-4

debian advisories DEBIAN-CVE-2021-3426

  • python3.6 Ubuntu 18.04 LTS 3.6.9-1~18.04ubuntu1.7
  • python3.9 Ubuntu 20.04 LTS 3.9.5-3~20.04.1
  • python3.4 Ubuntu Pro 14.04 LTS 3.4.3-1ubuntu1~14.04.7+esm12
  • python3.5 Ubuntu Pro 14.04 LTS 3.5.2-2ubuntu0~16.04.4~14.04.1+esm1
  • python3.5 Ubuntu Pro 16.04 LTS 3.5.2-2ubuntu0~16.04.13+esm2
  • python3.7 Ubuntu Pro 18.04 LTS 3.7.5-2ubuntu1~18.04.2+esm1
  • python3.8 Ubuntu Pro 18.04 LTS 3.8.0-3ubuntu1~18.04.2+esm2

ubuntu advisories UBUNTU-CVE-2021-3426

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • pytz RHEL 8 2019.3-3.module+el8.4.0+8888+89bc7e79
  • babel RHEL 8 2.7.0-11.module+el8.5.0+11015+9c1c7c42
  • numpy RHEL 8 1.17.3-6.module+el8.5.0+12205+a865257a
  • scipy RHEL 8 1.3.1-4.module+el8.4.0+8888+89bc7e79
  • Cython RHEL 8 0.29.14-4.module+el8.4.0+8888+89bc7e79
  • pytest RHEL 8 4.6.6-3.module+el8.4.0+8888+89bc7e79
  • PyYAML RHEL 8 5.4.1-1.module+el8.5.0+10721+14d8e0d5
  • mod_wsgi RHEL 8 4.6.8-3.module+el8.4.0+8888+89bc7e79

red hat advisories RHSA-2021:4162RHSA-2021:3254RHSA-2021:4160RHSA-2021:4399

  • python3 SLES 15 SP1-BCL, SLE Module for Basesystem 15 SP2, SLE Micro 5.1 +10 more 3.6.15-3.91.4
  • python3-core SLES 15 SP1-BCL, SLE Module for Development Tools 15 SP2, SLE Module for Basesystem 15 SP2 +11 more 3.6.15-3.91.3
  • python3 SLE Module for Basesystem 15 SP3 3.6.15-10.9.1
  • python3-core SLE Module for Development Tools 15 SP3, SLE Module for Basesystem 15 SP3 3.6.15-10.9.1
  • python36 SLES for SAP 12 SP5, SLES 12 SP5 3.6.15-11.1
  • python36-core SLES for SAP 12 SP5, SLES 12 SP5 3.6.15-11.1
  • python3 SLE Module for Basesystem 15 SP3, SLE Module for Basesystem 15 SP2, SLE Micro 5.0 3.6.13-3.81.2
  • python3-core SLE Module for Development Tools 15 SP3, SLE Module for Development Tools 15 SP2, SLE Module for Basesystem 15 SP3 +2 more 3.6.13-3.81.1

suse advisories SUSE-SU-2021:4015-2SUSE-SU-2021:4104-1SUSE-SU-2021:4015-1SUSE-SU-2021:3486-1SUSE-SU-2021:1557-1SUSE-SU-2021:1490-1

  • python315 openSUSE Tumbleweed 3.15.0~a1-1.1
  • python314 openSUSE Tumbleweed 3.14.0~a1-1.1
  • python313 openSUSE Tumbleweed 3.13.0~b3-1.1
  • python310 openSUSE Tumbleweed 3.10.0rc1-4.2
  • python36 openSUSE Tumbleweed 3.6.15-1.1
  • python38 openSUSE Tumbleweed 3.8.12-1.2
  • python39 openSUSE Tumbleweed 3.9.7-2.1
  • python311 openSUSE Tumbleweed 3.11.0b1-1.1

opensuse advisories openSUSE-SU-2025:15713-1openSUSE-SU-2024:14434-1openSUSE-SU-2024:14109-1openSUSE-SU-2024:11283-1openSUSE-SU-2024:11284-1openSUSE-SU-2024:11285-1

  • python38-py AlmaLinux 8 1.8.0-8.module_el8.6.0+2778+cd494b30
  • python38-ply AlmaLinux 8 3.11-10.module_el8.6.0+2778+cd494b30
  • python38-six AlmaLinux 8 1.12.0-10.module_el8.6.0+2778+cd494b30
  • python38-cffi AlmaLinux 8 1.13.2-3.module_el8.6.0+2778+cd494b30
  • python38-idna AlmaLinux 8 2.8-6.module_el8.6.0+2778+cd494b30
  • python38-pytz AlmaLinux 8 2019.3-3.module_el8.6.0+2778+cd494b30
  • python38-attrs AlmaLinux 8 19.3.0-3.module_el8.6.0+2778+cd494b30
  • python38-babel AlmaLinux 8 2.7.0-11.module_el8.6.0+2778+cd494b30

almalinux advisories ALSA-2021:4162ALSA-2021:4399ALSA-2021:4160

  • pytz Rocky Linux 8 2019.3-3.module+el8.4.0+570+c2eaf144
  • babel Rocky Linux 8 2.7.0-11.module+el8.5.0+672+ab6eb015
  • numpy Rocky Linux 8 1.17.3-6.module+el8.5.0+672+ab6eb015
  • scipy Rocky Linux 8 1.3.1-4.module+el8.5.0+672+ab6eb015
  • scipy Rocky Linux 8 1.3.1-4.module+el8.4.0+570+c2eaf144
  • Cython Rocky Linux 8 0.29.14-4.module+el8.4.0+570+c2eaf144
  • pytest Rocky Linux 8 4.6.6-3.module+el8.4.0+570+c2eaf144
  • PyYAML Rocky Linux 8 5.4.1-1.module+el8.5.0+672+ab6eb015

rocky linux advisories RLSA-2021:4162RLSA-2021:4160

  • python3 Alpine 3.24, Alpine 3.23, Alpine 3.22 +7 more 3.9.4-r0

alpine advisories ALPINE-CVE-2021-3426

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • python Arch Linux 3.9.3-1

arch linux advisories AVG-1675

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-2021-3426 updated cvss 5.7

python: Information disclosure via pydoc

  • Red Hat Enterprise Linux 7 python3, python3-idle, python3-libs, python3-test, python3-tkinter Red Hat Quay 3 quay/quay-rhel8
    affected: workaround, no fix planned “Use the console (no argument needed) or HTML file (-w argument) output to generate docs rather than the HTTP server options. Put differently, do not use the -p or -n options of pydoc.”
  • Red Hat CodeReady Linux Builder (v. 8) pytest 4.6.6-3.module+el8.4.0+8888+89bc7e79, pytest 6.0.2-2.module+el8.4.0+9822+20bf1249, Cython 0.29.21-5.module+el8.4.0+9822+20bf1249, pybind11 2.6.1-2.module+el8.4.0+9822+20bf1249, python-py 1.8.0-8.module+el8.4.0+8888+89bc7e79, python-py 1.10.0-1.module+el8.4.0+9822+20bf1249, +34 more Red Hat Enterprise Linux AppStream (v. 8) python3-idle 3.6.8-41.el8, python3-test 3.6.8-41.el8, platform-python 3.6.8-41.el8, python3-tkinter 3.6.8-41.el8, pytz 2019.3-3.module+el8.4.0+8888+89bc7e79, scipy 1.3.1-4.module+el8.4.0+8888+89bc7e79, +118 more
    fixed: vendor fix “Use the console (no argument needed) or HTML file (-w argument) output to generate docs rather than the HTTP server options. Put differently, do not use the -p or -n options of pydoc.” RHSA-2021:4162
  • Red Hat Enterprise Linux BaseOS (v. 8) python3 3.6.8-41.el8, python3-libs 3.6.8-41.el8, python3-test 3.6.8-41.el8, platform-python 3.6.8-41.el8
    fixed: vendor fix “Use the console (no argument needed) or HTML file (-w argument) output to generate docs rather than the HTTP server options. Put differently, do not use the -p or -n options of pydoc.” RHSA-2021:4399
  • Red Hat Software Collections for Red Hat Enterprise Linux Server (v. 7) rh-python38-babel 2.7.0-12.el7, rh-python38-python 3.8.11-2.el7, rh-python38-python-lxml 4.4.1-7.el7, rh-python38-python-pip 19.3.1-2.el7, rh-python38-python-idle 3.8.11-2.el7, rh-python38-python-libs 3.8.11-2.el7, +9 more Red Hat Software Collections for Red Hat Enterprise Linux Server EUS (v. 7.7) rh-python38-babel 2.7.0-12.el7, rh-python38-python 3.8.11-2.el7, rh-python38-python-lxml 4.4.1-7.el7, rh-python38-python-pip 19.3.1-2.el7, rh-python38-python-idle 3.8.11-2.el7, rh-python38-python-libs 3.8.11-2.el7, +9 more Red Hat Software Collections for Red Hat Enterprise Linux Workstation (v. 7) rh-python38-babel 2.7.0-12.el7, rh-python38-python 3.8.11-2.el7, rh-python38-python-lxml 4.4.1-7.el7, rh-python38-python-pip 19.3.1-2.el7, rh-python38-python-idle 3.8.11-2.el7, rh-python38-python-libs 3.8.11-2.el7, +9 more
    fixed: vendor fix “Use the console (no argument needed) or HTML file (-w argument) output to generate docs rather than the HTTP server options. Put differently, do not use the -p or -n options of pydoc.” RHSA-2021:3254
  • Red Hat Enterprise Linux 6 python, tkinter, python-libs, python-test, python-tools Red Hat Enterprise Linux 7 python, tkinter, python-libs, python-test, python-tools Red Hat Enterprise Linux 8 scipy, python2, python36, python-nose, python-wheel, python2-libs, +24 more Red Hat Software Collections python27-python, python27-tkinter, python27-python-libs, python27-python-test, python27-python-tools
    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 ICSA-23-348-10 updated cvss 5.7

Siemens SIMATIC S7-1500

  • Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0) >= 3.1.0, < 3.1.5 Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0) >= 3.1.0, < 3.1.5 Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0) >= 3.1.0, < 3.1.5 Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0) >= 3.1.0, < 3.1.5 Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0) >= 3.1.0, < 3.1.5
    affected: fixed in V3.1.5, mitigation support.industry.siemens.com

Facts from CISA's republication of the vendor's own advisory (CSAF); the linked advisory is the authoritative source. CISA notification · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
10 mo ago

Exploit prediction

1.86% chance of exploitation in the next 30 days, higher than 79% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CISA ADP 3.1 5.7 CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
NVD 3.1 5.7 CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
CNA 3.1 5.7 CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
NVD 2.0 2.7 AV:A/AC:L/Au:S/C:P/I:N/A:N
OSV 3.1 5.7 CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

Affected packages

ecosystem package affected fixed in
bitnami libpython
<2.7.18
>=3.6.0, <3.6.13
>=3.7.0, <3.7.10
>=3.8.0, <3.8.8
>=3.9.0, <3.9.3
2.7.18
3.6.13
3.7.10
3.8.8
3.9.3
bitnami python
<2.7.18
>=3.6.0, <3.6.13
>=3.7.0, <3.7.10
>=3.8.0, <3.8.8
>=3.9.0, <3.9.3
2.7.18
3.6.13
3.7.10
3.8.8
3.9.3
bitnami python-min
<2.7.18
>=3.6.0, <3.6.13
>=3.7.0, <3.7.10
>=3.8.0, <3.8.8
>=3.9.0, <3.9.3
2.7.18
3.6.13
3.7.10
3.8.8
3.9.3

Affected products

  • n/a python
  • Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP
  • Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP
  • Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP

Classification

Weakness
  • CWE-200 Exposure of Sensitive Information to an Unauthorized Actor
  • CWE-22 Improper Limitation of a Pathname to a Restricted Directory

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.