CVE-2020-3811Public exploitNetwork attack vector

Unauthenticated mail-address verification bypass via uninitialized domain

Published May 26, 2020 · Updated Sep 17, 2024

Mail-address verification bypass in Debian netqmail 1.06 allows remote attackers to submit unqualified recipient addresses as valid. qmail-verify omits control_init(), retains the hard-coded default domain envnoathost, and treats unqualified addresses in that unverifiable domain as valid. No authentication is required; the bypass permits recipient addresses that should be rejected, without reported confidentiality or availability impact.

CVSS severity7.5
High
EPSS probability1.77%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Mail-address verification bypass in Debian netqmail 1.06 allows remote attackers to submit unqualified recipient addresses as valid. qmail-verify omits control_init(), retains the hard-coded default domain envnoathost, and treats unqualified addresses in that unverifiable domain as valid. No authentication is required; the bypass permits recipient addresses that should be rejected, without reported confidentiality or availability impact.

The record

CVE
CVE-2020-3811
Published
May 26, 2020
Updated
Sep 17, 2024
Vendor
Debian
Product
netqmail
Classifications
CWE-665, CWE-863, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 26, 2020CVE publishedPublication date reported by the CVE source.
  2. Sep 17, 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?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=1.06

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Debian · netqmailversion=1.06

Published CVSS scores

5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:P/A:N
7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/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.

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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-665Improper Initialization
CWE-863Incorrect Authorization
T1190Exploit Public-Facing Application

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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