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Not in CISA KEV
HIGH severity

CVE-2020-13163 — em-imap

HIGH

CVE-2020-13163 is a high-severity (CVSS 7.4) CWE-295 vulnerability in em-imap. 2 public exploit references exist, so weaponization risk is real. No vendor fix is recorded yet; mitigation options are listed below.

Improper certificate validation in em-imap

Also known asGHSA-4f68-49qq-h392
Published
Updated
Affected
1 pkg
Patched
See advisory
Exploits
2 known
Exploitation data as of Oct 10, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
0.8%probability of exploitation in next 30 days
Lower Risk+0.02%
Lower risk than most CVEs54th percentile — riskier than 54% of all scored CVEsHighest risk
0.00%0.42%0.85%1.27%0.1%0.8%Apr 26Aug 26Oct 26

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

How urgent is this, really

CVE-2020-13163 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 385,987 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

1 pkg affected
💎em-imap

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

Description

em-imap 0.5 and earlier use the library eventmachine in an insecure way that allows an attacker to perform a man-in-the-middle attack against users of the library. The hostname in a TLS server certificate is not verified.

Affected Packages

1 total
EcosystemPackageVulnerable rangeFix
💎RubyGemsem-imapall versionsNo fix

Affected Products

1 product · 1 configurations
Application
em-imapem-imap_project
1 version
0.5
Exploits & PoCs
2

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

em-imap 0.5 uses the library eventmachine in an insecure way that allows…

github.comNVDMar 2021

em-imap 0.5 uses the library eventmachine in an insecure way that allows…

securitylab.github.comNVDMar 2021

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for em-imap, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Remediation status

    No patched version of em-imap has shipped for CVE-2020-13163 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.

  3. Mitigate without a patch

    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

em-imap 0.5 and earlier use the library eventmachine in an insecure way that allows an attacker to perform a man-in-the-middle attack against users of the library. The hostname in a TLS server certificate is not verified.
O3 Security · Impact-Aware SCA

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CVE-2020-13163: em-imap: Improper certificate validation