CVE-2019-12855: Twisted Improper Certificate Validation Vulnerability

CRITICAL
Advisory Identifier: GHSA-65rm-h285-5cc5
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CVSS 7.4
CWE-295
Published
Advisory Summary

CVE-2019-12855 is a CRITICAL (CVSS 7.4) improper certificate validation vulnerability (CWE-295: Improper Certificate Validation) affecting Twisted libraries in the PyPI ecosystem. The issue involves improper certificate validation in twisted. Remediation is available by upgrading affected packages to version 19.7.0rc1.

CVE-2019-12855 at a Glance

CVE Identifier CVE-2019-12855
GHSA Identifier GHSA-65rm-h285-5cc5
Severity CRITICAL
CVSS v3.1 Base Score 7.4
CWE Classification CWE-295: Improper Certificate Validation
Affected Product Twisted
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 7.4

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/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 High (I:H)
Availability None (A:N)

How to Fix CVE-2019-12855

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

Twisted fixed: 19.7.0rc1 
pip install Twisted>=19.7.0rc1
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 Twisted

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2019-12855, inspect your installed packages using pip:

pip show Twisted

Analyze the terminal output to locate any version of Twisted in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 19.7.0rc1), your application is affected.

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

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-295: Improper Certificate Validation, where the product does not validate, or incorrectly validates, a certificate. In Twisted, 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

In words.protocols.jabber.xmlstream in Twisted through 19.2.1, XMPP support did not verify certificates when used with TLS, allowing an attacker to MITM connections.

CVE-2019-12855 Affected Twisted Versions

1 component(s)
Fixed Versions:
19.7.0rc1
Product / Package Ecosystem Affected Versions Fixed Version
Twisted
pypi/Twisted
PyPI
< 19.7.0rc1
19.7.0rc1

References

NVD — CVE-2019-12855 NVD
https://nvd.nist.gov/vuln/detail/CVE-2019-12855
Twisted Source Repository REPOSITORY
https://github.com/twisted/twisted/pull/1147
Twisted Source Repository REPOSITORY
https://github.com/pypa/advisory-database/tree/main/vulns/twisted/PYSEC-2019-129.yaml
Twisted Source Repository REPOSITORY
https://github.com/twisted/twisted
lists.fedoraproject.org/archives/list/packa... WEB
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/PLTZDMFBNFSJMBXYJNGJHENJA4H2TSMZ
lists.fedoraproject.org/archives/list/packa... WEB
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/PLTZDMFBNFSJMBXYJNGJHENJA4H2TSMZ
Twisted Security Information SECURITY
https://twistedmatrix.com/trac/ticket/9561
usn.ubuntu.com/4308-1 WEB
https://usn.ubuntu.com/4308-1
usn.ubuntu.com/4308-2 WEB
https://usn.ubuntu.com/4308-2
Twisted Security Information SECURITY
https://www.oracle.com/security-alerts/cpuapr2020.html
Twisted Security Information SECURITY
http://lists.opensuse.org/opensuse-security-announce/2019-09/msg00013.html
Twisted Security Information SECURITY
http://lists.opensuse.org/opensuse-security-announce/2019-09/msg00028.html

Frequently Asked Questions

What is CVE-2019-12855?
CVE-2019-12855 is a security vulnerability in Twisted involving Improper Certificate Validation in Twisted under CWE-295: Improper Certificate Validation.
Which Twisted versions are affected?
Affected versions include releases prior to 19.7.0rc1 across affected packages: Twisted.
What version fixes CVE-2019-12855?
Upgrading to 19.7.0rc1 (or the latest patched release for your respective branch) resolves the vulnerability.
Is Twisted affected?
Yes, Twisted is affected in releases prior to 19.7.0rc1. Upgrade your dependency to 19.7.0rc1 or later.
What is the CVSS score of CVE-2019-12855?
CVE-2019-12855 has a CVSS v3.1 base score of 7.4 (CRITICAL) with vector string CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N.
What CWE is associated with CVE-2019-12855?
CVE-2019-12855 is classified under CWE-295: Improper Certificate Validation (The product does not validate, or incorrectly validates, a certificate.).
How can I check PyPI dependencies for CVE-2019-12855?
Run the dependency tree command: 'pip show Twisted'. 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-65rm-h285-5cc5",
  "modified" : "2024-11-25T19:24:13Z",
  "published" : "2019-08-16T14:02:35Z",
  "aliases" : [ "CVE-2019-12855" ],
  "summary" : "Improper Certificate Validation in Twisted",
  "details" : "In words.protocols.jabber.xmlstream in Twisted through 19.2.1, XMPP support did not verify certificates when used with TLS, allowing an attacker to MITM connections.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N"
  }, {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "Twisted"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "19.7.0rc1"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2019-12855"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/twisted/twisted/pull/1147"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/pypa/advisory-database/tree/main/vulns/twisted/PYSEC-2019-129.yaml"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/twisted/twisted"
  }, {
    "type" : "WEB",
    "url" : "https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/PLTZDMFBNFSJMBXYJNGJHENJA4H2TSMZ"
  }, {
    "type" : "WEB",
    "url" : "https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/PLTZDMFBNFSJMBXYJNGJHENJA4H2TSMZ"
  }, {
    "type" : "WEB",
    "url" : "https://twistedmatrix.com/trac/ticket/9561"
  }, {
    "type" : "WEB",
    "url" : "https://usn.ubuntu.com/4308-1"
  }, {
    "type" : "WEB",
    "url" : "https://usn.ubuntu.com/4308-2"
  }, {
    "type" : "WEB",
    "url" : "https://www.oracle.com/security-alerts/cpuapr2020.html"
  }, {
    "type" : "WEB",
    "url" : "http://lists.opensuse.org/opensuse-security-announce/2019-09/msg00013.html"
  }, {
    "type" : "WEB",
    "url" : "http://lists.opensuse.org/opensuse-security-announce/2019-09/msg00028.html"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-295" ],
    "severity" : "CRITICAL",
    "github_reviewed" : true,
    "github_reviewed_at" : "2019-08-12T15:06:23Z",
    "nvd_published_at" : "2019-06-16T12:29:00Z"
  }
}