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Fencer Vulns
high 7.5

CVE-2020-13757 json

Python-RSA decryption of ciphertext leads to DoS

published 2020-06-01 6 y ago modified 2026-06-17 4 mo ago also GHSA-537h-rv9q-vvph , PYSEC-2020-99 , EUVD-2020-0168

cvss
7.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
1.4%
EPSS 1.4% chance of exploitation in 30 days, percentile 73%
public exploits
0
none known

Summary

Python-RSA before 4.1 ignores leading '\0' bytes during decryption of ciphertext. This could conceivably have a security-relevant impact, e.g., by helping an attacker to infer that an application uses Python-RSA, or if the length of accepted ciphertext affects application behavior (such as by causing excessive memory allocation).

Patch / fix

  • pypi rsa 4.1
  • python-rsa_project python-rsa 4.1
  • python-rsa Debian 14, Debian 13, Debian 12 4.7.2-1

debian advisories DEBIAN-CVE-2020-13757

  • python-rsa Ubuntu Pro 14.04 LTS 3.1.2-1ubuntu0.1+esm1
  • python-rsa Ubuntu Pro 16.04 LTS 3.2.3-1.1ubuntu0.1~esm1
  • python-rsa Ubuntu Pro 18.04 LTS 3.4.2-1ubuntu0.1~esm1

ubuntu advisories UBUNTU-CVE-2020-13757

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

  • jenkins openshift 3.11 2.235.2.1597220898-1.el7
  • python-rsa openshift 3.11 4.5-2.el7
  • python2-rsa openshift 3.11 4.5-2.el7
  • jenkins-2-plugins openshift 3.11 3.11.1597310986-1.el7
  • openshift-ansible openshift 3.11 3.11.272-1.git.0.79ab6e9.el7
  • openshift-ansible-test openshift 3.11 3.11.272-1.git.0.79ab6e9.el7
  • openshift-ansible-roles openshift 3.11 3.11.272-1.git.0.79ab6e9.el7
  • openshift-ansible-playbooks openshift 3.11 3.11.272-1.git.0.79ab6e9.el7

red hat advisories RHSA-2020:3541RHSA-2020:3453

  • python-rsa OpenStack Cloud Crowbar 8, OpenStack Cloud 8, HPE Helion OpenStack 8 3.4.2-3.3.1
  • python-rsa OpenStack Cloud Crowbar 9, OpenStack Cloud 9 3.4.2-4.4.1
  • python-rsa SLE Module for Public Cloud 12, OpenStack Cloud 7 3.1.4-12.16.1
  • python-rsa SLES for SAP 15 SP1, SLES 15 SP1-LTSS, SLES 15 SP1-BCL +11 more 3.4.2-3.4.1

suse advisories SUSE-SU-2022:3287-1SUSE-SU-2021:2253-1SUSE-SU-2021:2237-1SUSE-SU-2021:2008-1

  • python-rsa openSUSE Tumbleweed 4.9.1-1.4
  • python-rsa openSUSE Tumbleweed 4.9-3.5
  • python-rsa openSUSE Tumbleweed 4.7.2-1.5
  • python-rsa openSUSE Leap 15.3 3.4.2-3.4.1
  • python-rsa openSUSE Leap 15.2 3.4.2-lp152.4.3.1

opensuse advisories openSUSE-SU-2026:12041-1openSUSE-SU-2024:14163-1openSUSE-SU-2024:11269-1openSUSE-SU-2021:2008-1openSUSE-SU-2021:0901-1

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-2020-13757 updated cvss 7.5

python-rsa: decryption of ciphertext leads to DoS

  • Red Hat Ceph Storage 4 python-rsa, python3-rsa
    affected: no fix available
  • Red Hat OpenStack Platform 13 (Queens) python2-rsa Red Hat OpenStack Platform 15 (Stein) python3-rsa Red Hat OpenStack Platform 16 (Train) python-rsa, python3-rsa
    affected: no fix planned “Will not fix”
  • Red Hat Quay 3 python-rsa
    affected: no fix available
  • Red Hat OpenShift Container Platform 3.11 python-rsa 4.5-2.el7, python2-rsa 4.5-2.el7
    fixed: vendor fix RHSA-2020:3541
  • Red Hat OpenShift Container Platform 4.5 python-rsa 4.5-1.el7, python2-rsa 4.5-1.el7
    fixed: vendor fix RHSA-2020:3453
  • Red Hat OpenShift Container Platform 3.11 jenkins 2.235.2.1597220898-1.el7, jenkins-2-plugins 3.11.1597310986-1.el7, openshift-ansible 3.11.272-1.git.0.79ab6e9.el7, openshift-ansible-test 3.11.272-1.git.0.79ab6e9.el7, openshift-ansible-roles 3.11.272-1.git.0.79ab6e9.el7, openshift-ansible-playbooks 3.11.272-1.git.0.79ab6e9.el7 Red Hat OpenShift Container Platform 4.5 jenkins-2-plugins 4.5.1596698303-1.el7
    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

Exploit prediction

1.42% chance of exploitation in the next 30 days, higher than 73% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/sybrenstuvel/python-rsa/issues/146#issuecomment-641845667 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
NVD 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
NVD 2.0 5.0 AV:N/AC:L/Au:N/C:P/I:N/A:N
GitHub 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Affected packages

ecosystem package affected fixed in
pypi rsa
<4.1
4.1

Classification

Weakness
  • CWE-327 Use of a Broken or Risky Cryptographic Algorithm

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.