CVE-2020-13163Public exploitNetwork attack vector

Server impersonation via missing TLS hostname validation

Published May 19, 2020 · Updated Aug 4, 2024

Improper certificate validation in em-imap 0.5 allows man-in-the-middle attackers to impersonate trusted IMAP servers. Its EventMachine TLS connection accepts a server certificate without comparing the certificate hostname with the requested IMAP host. An attacker able to intercept or redirect the network connection can impersonate the server and supply malicious data through a session the client treats as trusted.

CVSS severity7.4
High
EPSS probability0.75%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper certificate validation in em-imap 0.5 allows man-in-the-middle attackers to impersonate trusted IMAP servers. Its EventMachine TLS connection accepts a server certificate without comparing the certificate hostname with the requested IMAP host. An attacker able to intercept or redirect the network connection can impersonate the server and supply malicious data through a session the client treats as trusted.

The record

CVE
CVE-2020-13163
Published
May 19, 2020
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-295, CWE-297, T1557
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 19, 2020CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

7.4NIST National Vulnerability DatabaseCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
5.8NIST National Vulnerability DatabaseAV:N/AC:M/Au:N/C:P/I:P/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-295Improper Certificate Validation
CWE-297Improper Validation of Certificate with Host Mismatch
T1557Adversary-in-the-Middle

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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