PatchTheCVECVE-2020-13757: Python-RSA before 4.1 ignores leading '\0' bytes during decryption of ciphertext
CVE-2020-13757 is a high-severity flaw (CVSS 7.5) affecting python-rsa, fedora, ubuntu linux. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
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).
Why this priority
- High severity
- Public exploit reference
- Remotely exploitable, no login, no user action
- On your watchlist
A fixed release or distro patch exists.
Risk facts
| CVSS score | 7.5 (High) |
| Attack vector | Network (remote) |
| Attack complexity | Low |
| Privileges needed | None |
| User interaction | None |
| EPSS exploit chance | 1.4% (top 27%) |
| CISA exploited list | No |
| Weakness | CWE-327 |
| Published | 2020-06-01 |
| Last modified | 2026-06-17 |
Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score
Am I affected?
Timeline
- Published CVE record published
- Updated Record last modified
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.
Quick answers
How do I fix CVE-2020-13757?
python-rsa: upgrade to 4.1; fedora: mitigate or apply the listed mitigation; ubuntu linux: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.
Is CVE-2020-13757 being exploited?
CVE-2020-13757 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.
What does CVE-2020-13757 affect?
CVE-2020-13757 affects python-rsa, fedora, ubuntu linux. Severity is high (CVSS 7.5). 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 accepte
How urgent is CVE-2020-13757?
Priority 60/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action; On your watchlist
Software pages
Python vulnerabilities · Ubuntu vulnerabilities
Related CVEs
- CVE-2020-25658 HIGH 7.5 UPGRADE DOWNGRADE It was found that python-rsa is vulnerable to Bleichenbacher timing attacks