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MEDIUM severity

CVE-2020-2253 — email-ext

MEDIUMFix: jenkinsci/email-ext-plugin@ac039ba

CVE-2020-2253 is a medium-severity (CVSS 4.8) CWE-295 vulnerability in org.jenkins-ci.plugins:email-ext. A fix is available for org.jenkins-ci.plugins:email-ext — see the affected versions and patch details below.

Missing hostname validation in Email Extension Plugin

Also known asGHSA-4qrj-99r6-jfrh
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Oct 22, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
0.7%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs52th percentile — riskier than 52% of all scored CVEsHighest risk
0.00%0.40%0.79%1.19%0.0%0.7%Apr 26Aug 26Oct 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected
☕org.jenkins-ci.plugins:email-ext

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.

Description

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.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
☕Mavenorg.jenkins-ci.plugins:email-extall versions2.76org.jenkins-ci.plugins:email-ext:2.76

Affected Products

1 product · 1 configurations
Application
email extensionjenkins
≤ 2.75
range

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.jenkins-ci.plugins:email-ext, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update org.jenkins-ci.plugins:email-ext to 2.76 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-2253 is resolved across your whole dependency graph.

  3. Workarounds

    If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

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
O3 Security · Impact-Aware SCA

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CVE-2020-2253: email-ext — Fixed in 2.76