CVE-2020-14154Network attack vector

Connection interception via ignored certificate rejection

Published Jun 15, 2020 · Updated Aug 4, 2024

Improper certificate validation in Mutt before 1.14.3 allows man-in-the-middle attackers to intercept a GnuTLS-protected connection. The GnuTLS certificate-prompting path treats rejection of an expired intermediate certificate as nonterminal and continues establishing the connection. Exploitation requires a server certificate chain with an expired intermediate and a user who explicitly rejects that certificate; the resulting connection permits mail traffic to be read or altered.

CVSS severity4.8
Medium
EPSS probability1.06%
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 Mutt before 1.14.3 allows man-in-the-middle attackers to intercept a GnuTLS-protected connection. The GnuTLS certificate-prompting path treats rejection of an expired intermediate certificate as nonterminal and continues establishing the connection. Exploitation requires a server certificate chain with an expired intermediate and a user who explicitly rejects that certificate; the resulting connection permits mail traffic to be read or altered.

The record

CVE
CVE-2020-14154
Published
Jun 15, 2020
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
T1557
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 15, 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

4.8NIST NVDCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N
5.8NIST NVDAV: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 exploitUnconfirmed

Weakness, pattern, technique

T1557Adversary-in-the-Middle

Public exploit references

No public exploit references are available in this record.

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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