CVE-2020-28011Public exploit

Local process crash via unbounded selector formatting

Published May 6, 2021 · Updated Aug 4, 2024

Heap-based buffer overflow in queue_run() in Exim before 4.94.2 allows local users with exim privileges to crash the process via -R or -S options. queue_run() appends attacker-controlled deliver_selectstring or deliver_selectstring_sender values to big_buffer with unbounded sprintf calls. The published proof of concept aborts Exim; root escalation requires prior exim-account access and has not been demonstrated.

CVSS severity7.8
High
EPSS probability0.39%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Heap-based buffer overflow in queue_run() in Exim before 4.94.2 allows local users with exim privileges to crash the process via -R or -S options. queue_run() appends attacker-controlled deliver_selectstring or deliver_selectstring_sender values to big_buffer with unbounded sprintf calls. The published proof of concept aborts Exim; root escalation requires prior exim-account access and has not been demonstrated.

The record

CVE
CVE-2020-28011
Published
May 6, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-787, T1068
Attack vector
local
Privileges
authenticated

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 vectorlocal
Required privilegesauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

7.8NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
7.2NIST NVDAV:L/AC:L/Au:N/C:C/I:C/A:C

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)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-787Out-of-bounds Write
T1068Exploitation for Privilege Escalation

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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