CVE-2020-2253: Email ext Missing Hostname Validation Vulnerability

MODERATE
Advisory Identifier: GHSA-4qrj-99r6-jfrh
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CVSS 4.8
CWE-295
Published
Advisory Summary

CVE-2020-2253 is a MODERATE (CVSS 4.8) missing hostname validation vulnerability (CWE-295: Improper Certificate Validation) affecting Email ext libraries in the Maven ecosystem. The issue involves missing hostname validation in email extension plugin. Remediation is available by upgrading affected packages to version 2.76.

CVE-2020-2253 at a Glance

CVE Identifier CVE-2020-2253
GHSA Identifier GHSA-4qrj-99r6-jfrh
Severity MODERATE
CVSS v3.1 Base Score 4.8
CWE Classification CWE-295: Improper Certificate Validation
Affected Product Email ext
Package Ecosystem Maven
Published Date
Last Updated

Security Impact

CVSS: 4.8

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:L/I:L/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 Low (C:L)
Integrity Low (I:L)
Availability None (A:N)

How to Fix CVE-2020-2253

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

org.jenkins-ci.plugins:email-ext fixed: 2.76 
<dependency>
    <groupId>org.jenkins-ci.plugins</groupId>
    <artifactId>email-ext</artifactId>
    <version>2.76</version>
</dependency>
Verify Direct and Transitive Dependencies

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

mvn dependency:tree -Dincludes=org.jenkins-ci.plugins

How to Check if You Are Affected

To determine whether your Java application is affected by CVE-2020-2253, inspect your build dependencies using the Maven Dependency Plugin:

mvn dependency:tree -Dincludes=org.jenkins-ci.plugins

Analyze the terminal output to locate any version of Email ext in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 2.76), your application is affected.

Note: The mvn dependency:tree -Dincludes=org.jenkins-ci.plugins command inspects the resolved dependency graph declared in your project's POM files; it does not perform automated security scanning or inspect runtime dynamic classpaths. Always verify runtime container classpaths and shaded JARs.

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 Email ext, 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

Email Extension Plugin 2.75 and earlier does not perform hostname validation when connecting to the configured SMTP server. This lack of validation could be abused using a man-in-the-middle attack to intercept these connections. Email Extension Plugin 2.76 validates the SMTP hostname when connecting via TLS by default. In Email Extension Plugin 2.75 and earlier, administrators can set the Java system property `mail.smtp.ssl.checkserveridentity` to `true` on startup to enable this protection. Alternatively, this protection can be enabled (or disabled in the new version) via the 'Advanced Email Properties' field in the plugin’s configuration in Configure System. In case of problems, this protection can be disabled again by setting `mail.smtp.ssl.checkserveridentity` to `false` using either method.

CVE-2020-2253 Affected Email ext Versions

1 component(s)
Fixed Versions:
2.76
Product / Package Ecosystem Affected Versions Fixed Version
org.jenkins-ci.plugins:email-ext
maven/org.jenkins-ci.plugins/email-ext
Maven
< 2.76
2.76

References

NVD — CVE-2020-2253 NVD
https://nvd.nist.gov/vuln/detail/CVE-2020-2253
Security Fix Commit FIX COMMIT
https://github.com/jenkinsci/email-ext-plugin/commit/ac039ba581f5946975a327709ff201b459900caa
Email ext Source Repository REPOSITORY
https://github.com/jenkinsci/email-ext-plugin
Email ext Security Information SECURITY
https://www.jenkins.io/security/advisory/2020-09-16/#SECURITY-1851
Email ext Security Information SECURITY
http://www.openwall.com/lists/oss-security/2020/09/16/3

Frequently Asked Questions

What is CVE-2020-2253?
CVE-2020-2253 is a security vulnerability in Email ext involving Missing hostname validation in Email Extension Plugin under CWE-295: Improper Certificate Validation.
Which Email ext versions are affected?
Affected versions include releases prior to 2.76 across affected packages: org.jenkins-ci.plugins:email-ext.
What version fixes CVE-2020-2253?
Upgrading to 2.76 (or the latest patched release for your respective branch) resolves the vulnerability.
Is email-ext affected?
Yes, org.jenkins-ci.plugins:email-ext is affected in releases prior to 2.76. Upgrade your dependency to 2.76 or later.
What is the CVSS score of CVE-2020-2253?
CVE-2020-2253 has a CVSS v3.1 base score of 4.8 (MODERATE) with vector string CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N.
What CWE is associated with CVE-2020-2253?
CVE-2020-2253 is classified under CWE-295: Improper Certificate Validation (The product does not validate, or incorrectly validates, a certificate.).
How can I check Maven dependencies for CVE-2020-2253?
Run the dependency tree command: 'mvn dependency:tree -Dincludes=org.jenkins-ci.plugins'. 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-4qrj-99r6-jfrh",
  "modified" : "2023-12-14T10:03:59Z",
  "published" : "2022-05-24T17:28:24Z",
  "aliases" : [ "CVE-2020-2253" ],
  "summary" : "Missing hostname validation in Email Extension Plugin",
  "details" : "Email Extension Plugin 2.75 and earlier does not perform hostname validation when connecting to the configured SMTP server. This lack of validation could be abused using a man-in-the-middle attack to intercept these connections.\n\nEmail Extension Plugin 2.76 validates the SMTP hostname when connecting via TLS by default. In Email Extension Plugin 2.75 and earlier, administrators can set the Java system property `mail.smtp.ssl.checkserveridentity` to `true` on startup to enable this protection. Alternatively, this protection can be enabled (or disabled in the new version) via the 'Advanced Email Properties' field in the plugin’s configuration in Configure System.\n\nIn case of problems, this protection can be disabled again by setting `mail.smtp.ssl.checkserveridentity` to `false` using either method.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "org.jenkins-ci.plugins:email-ext"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "2.76"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 2.75"
    }
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2020-2253"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/jenkinsci/email-ext-plugin/commit/ac039ba581f5946975a327709ff201b459900caa"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/jenkinsci/email-ext-plugin"
  }, {
    "type" : "WEB",
    "url" : "https://www.jenkins.io/security/advisory/2020-09-16/#SECURITY-1851"
  }, {
    "type" : "WEB",
    "url" : "http://www.openwall.com/lists/oss-security/2020/09/16/3"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-295" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2022-12-29T01:29:38Z",
    "nvd_published_at" : "2020-09-16T14:15:00Z"
  }
}