CVE-2021-39272Network attack vector

Cleartext mail disclosure via skipped STARTTLS enforcement

Published Aug 30, 2021 · Updated Aug 4, 2024

TLS policy bypass in Fetchmail 6.4.21 and earlier allows remote attackers to expose retrieved mail through cleartext IMAP or POP3 sessions. The protocol state machine skips STARTTLS but continues when IMAP PREAUTH enters an authenticated state, POP3 RPA is advertised for a Compuserve host, or auth ssh is configured. Exploitation requires one of these non-default paths and exposes session data to malicious servers or man-in-the-middle attackers without allowing alteration.

CVSS severity5.9
Medium
EPSS probability0.92%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

TLS policy bypass in Fetchmail 6.4.21 and earlier allows remote attackers to expose retrieved mail through cleartext IMAP or POP3 sessions. The protocol state machine skips STARTTLS but continues when IMAP PREAUTH enters an authenticated state, POP3 RPA is advertised for a Compuserve host, or auth ssh is configured. Exploitation requires one of these non-default paths and exposes session data to malicious servers or man-in-the-middle attackers without allowing alteration.

The record

CVE
CVE-2021-39272
Published
Aug 30, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-319, T1557
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 30, 2021CVE 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

5.9NIST NVDCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
4.3NIST NVDAV:N/AC:M/Au:N/C:P/I:N/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

CWE-319Cleartext Transmission of Sensitive Information
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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