CVE-2020-25658: Rsa Timing Attacks Vulnerability

HIGH
Advisory Identifier: GHSA-xrx6-fmxq-rjj2
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CVSS 5.9
CWE-385 CWE-327
Published
Advisory Summary

CVE-2020-25658 is a HIGH (CVSS 5.9) timing attacks vulnerability (CWE-385: Covert Timing Channel) affecting Rsa libraries in the PyPI ecosystem. The issue involves timing attacks in python-rsa. Remediation is available by upgrading affected packages to version 4.7.

CVE-2020-25658 at a Glance

CVE Identifier CVE-2020-25658
GHSA Identifier GHSA-xrx6-fmxq-rjj2
Severity HIGH
CVSS v3.1 Base Score 5.9
CWE Classification CWE-385: Covert Timing Channel
Affected Product Rsa
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 5.9

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N).

Attack Vector Network (AV:N)
Attack Complexity High (AC:H)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality High (C:H)
Integrity None (I:N)
Availability None (A:N)

How to Fix CVE-2020-25658

To remediate this vulnerability, upgrade all affected Rsa dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

rsa fixed: 4.7 
pip install rsa>=4.7
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

pip show rsa

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2020-25658, inspect your installed packages using pip:

pip show rsa

Analyze the terminal output to locate any version of Rsa in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 4.7), your application is affected.

Note: The pip show rsa command checks currently installed packages in your active Python environment.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-385: Covert Timing Channel, where covert timing channels convey information by modulating some aspect of system behavior over time, so that the program receiving the information can observe system behavior and infer protected information. In Rsa, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

It was found that python-rsa is vulnerable to Bleichenbacher timing attacks. An attacker can use this flaw via the RSA decryption API to decrypt parts of the cipher text encrypted with RSA

CVE-2020-25658 Affected Rsa Versions

1 component(s)
Fixed Versions:
4.7
Product / Package Ecosystem Affected Versions Fixed Version
rsa
pypi/rsa
PyPI
≥ 2.1
< 4.7
4.7

References

NVD — CVE-2020-25658 NVD
https://nvd.nist.gov/vuln/detail/CVE-2020-25658
Rsa Source Repository REPOSITORY
https://github.com/sybrenstuvel/python-rsa/issues/165
Security Fix Commit FIX COMMIT
https://github.com/sybrenstuvel/python-rsa/commit/dae8ce0d85478e16f2368b2341632775313d41ed
Rsa Security Information SECURITY
https://access.redhat.com/security/cve/CVE-2020-25658
bugzilla.redhat.com/show_bug.cgi WEB
https://bugzilla.redhat.com/show_bug.cgi?id=1889972
bugzilla.redhat.com/show_bug.cgi WEB
https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2020-25658
GitHub Advisory / Wiki ADVISORY
https://github.com/advisories/GHSA-xrx6-fmxq-rjj2
Rsa Source Repository REPOSITORY
https://github.com/pypa/advisory-database/tree/main/vulns/rsa/PYSEC-2020-100.yaml
Rsa Source Repository REPOSITORY
https://github.com/sybrenstuvel/python-rsa
access.redhat.com/errata/rhsa-2022:17... WEB
https://access.redhat.com/errata/RHSA-2022:1716
access.redhat.com/errata/rhsa-2021:06... WEB
https://access.redhat.com/errata/RHSA-2021:0637
lists.fedoraproject.org/archives/list/packa... WEB
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/2SAF67KDGSOHLVFTRDOHNEAFDRSSYIWA
lists.fedoraproject.org/archives/list/packa... WEB
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/APF364QJ2IYLPDNVFBOEJ24QP2WLVLJP
lists.fedoraproject.org/archives/list/packa... WEB
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QY4PJWTYSOV7ZEYZVMYIF6XRU73CY6O7
lists.fedoraproject.org/archives/list/packa... WEB
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/2SAF67KDGSOHLVFTRDOHNEAFDRSSYIWA
lists.fedoraproject.org/archives/list/packa... WEB
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/APF364QJ2IYLPDNVFBOEJ24QP2WLVLJP
lists.fedoraproject.org/archives/list/packa... WEB
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/QY4PJWTYSOV7ZEYZVMYIF6XRU73CY6O7
access.redhat.com/errata/rhsa-2020:56... WEB
https://access.redhat.com/errata/RHSA-2020:5634

Frequently Asked Questions

What is CVE-2020-25658?
CVE-2020-25658 is a security vulnerability in Rsa involving Timing attacks in python-rsa under CWE-385: Covert Timing Channel.
Which Rsa versions are affected?
Affected versions include releases prior to 4.7 across affected packages: rsa.
What version fixes CVE-2020-25658?
Upgrading to 4.7 (or the latest patched release for your respective branch) resolves the vulnerability.
Is rsa affected?
Yes, rsa is affected in releases prior to 4.7. Upgrade your dependency to 4.7 or later.
What is the CVSS score of CVE-2020-25658?
CVE-2020-25658 has a CVSS v3.1 base score of 5.9 (HIGH) with vector string CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N.
What CWE is associated with CVE-2020-25658?
CVE-2020-25658 is classified under CWE-385: Covert Timing Channel (Covert timing channels convey information by modulating some aspect of system behavior over time, so that the program receiving the information can observe system behavior and infer protected information.).
How can I check PyPI dependencies for CVE-2020-25658?
Run the dependency tree command: 'pip show rsa'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-xrx6-fmxq-rjj2",
  "modified" : "2024-10-26T22:33:21Z",
  "published" : "2021-04-30T17:35:15Z",
  "aliases" : [ "CVE-2020-25658" ],
  "summary" : "Timing attacks in python-rsa",
  "details" : "It was found that python-rsa is vulnerable to Bleichenbacher timing attacks. An attacker can use this flaw via the RSA decryption API to decrypt parts of the cipher text encrypted with RSA",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N"
  }, {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "rsa"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "2.1"
      }, {
        "fixed" : "4.7"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2020-25658"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/sybrenstuvel/python-rsa/issues/165"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/sybrenstuvel/python-rsa/commit/dae8ce0d85478e16f2368b2341632775313d41ed"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/security/cve/CVE-2020-25658"
  }, {
    "type" : "WEB",
    "url" : "https://bugzilla.redhat.com/show_bug.cgi?id=1889972"
  }, {
    "type" : "WEB",
    "url" : "https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2020-25658"
  }, {
    "type" : "ADVISORY",
    "url" : "https://github.com/advisories/GHSA-xrx6-fmxq-rjj2"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/pypa/advisory-database/tree/main/vulns/rsa/PYSEC-2020-100.yaml"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/sybrenstuvel/python-rsa"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/errata/RHSA-2022:1716"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/errata/RHSA-2021:0637"
  }, {
    "type" : "WEB",
    "url" : "https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/2SAF67KDGSOHLVFTRDOHNEAFDRSSYIWA"
  }, {
    "type" : "WEB",
    "url" : "https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/APF364QJ2IYLPDNVFBOEJ24QP2WLVLJP"
  }, {
    "type" : "WEB",
    "url" : "https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QY4PJWTYSOV7ZEYZVMYIF6XRU73CY6O7"
  }, {
    "type" : "WEB",
    "url" : "https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/2SAF67KDGSOHLVFTRDOHNEAFDRSSYIWA"
  }, {
    "type" : "WEB",
    "url" : "https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/APF364QJ2IYLPDNVFBOEJ24QP2WLVLJP"
  }, {
    "type" : "WEB",
    "url" : "https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/QY4PJWTYSOV7ZEYZVMYIF6XRU73CY6O7"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/errata/RHSA-2020:5634"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-327", "CWE-385" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2021-04-20T17:11:41Z",
    "nvd_published_at" : "2020-11-12T14:15:00Z"
  }
}