CVE-2020-28019Public exploitNetwork attack vector

Mail server crash via stale BDAT function pointer

Published May 6, 2021 · Updated Aug 4, 2024

Improper initialization in Exim 4.88 through 4.94.1 allows remote attackers to crash the mail server through an oversized BDAT message. After an over-limit message triggers an error, smtp_setup_msg re-enters while receive_getc still points to bdat_getc instead of the original input function. A second BDAT makes bdat_getc call itself until stack exhaustion terminates the process; no authentication or user interaction is required.

CVSS severity7.5
High
EPSS probability61.66%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper initialization in Exim 4.88 through 4.94.1 allows remote attackers to crash the mail server through an oversized BDAT message. After an over-limit message triggers an error, smtp_setup_msg re-enters while receive_getc still points to bdat_getc instead of the original input function. A second BDAT makes bdat_getc call itself until stack exhaustion terminates the process; no authentication or user interaction is required.

The record

CVE
CVE-2020-28019
Published
May 6, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-665, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 6, 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

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

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
T1499.004Endpoint Denial of Service: Application or System Exploitation

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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