CVE-2020-13757

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.4% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2020-06-01 · updated 2026-06-17
Weakness: CWE-327

Description

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).

Affected products

Canonical Ubuntu Linux: 14.04
Fedoraproject Fedora: 31, 32
Python-Rsa Project Python-Rsa: before 4.1 — fixed in 4.1

How to fix

Upgrade to a fixed version: Python-Rsa Project Python-Rsa 4.1. Check the vendor advisory for mitigations.

References

https://github.com/sybrenstuvel/python-rsa/issues/146
https://github.com/sybrenstuvel/python-rsa/issues/146#issuecomment-641845667
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/2KILTHBHNSDUCYV22ODLOKTICJJ7JQIQ/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ZYB65VNILRBTXL6EITQTH2PZPK7I23MW/
https://usn.ubuntu.com/4478-1/
https://github.com/sybrenstuvel/python-rsa/issues/146
https://github.com/sybrenstuvel/python-rsa/issues/146#issuecomment-641845667
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/2KILTHBHNSDUCYV22ODLOKTICJJ7JQIQ/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ZYB65VNILRBTXL6EITQTH2PZPK7I23MW/
https://usn.ubuntu.com/4478-1/

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