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CVE-2020-28024

29
FAUCET Score

CVE-2020-28024 is a critical buffer underwrite vulnerability in Exim versions prior to 4.94.2. This flaw allows unauthenticated remote attackers to execute arbitrary commands due to incorrect handling of non-character error codes by the smtp_ungetc function. With a CVSS score of 9.8 (Critical), it presents a severe risk with network-based attacks, low complexity, and complete compromise of confidentiality, integrity, and availability. While there is no known active exploitation or public exploit code (Metasploit, Nuclei, ExploitDB), the vulnerability has garnered significant community discussion and media coverage, indicating high awareness of its potential impact.

Impacted Technologies

VendorProductVersion(s)CPE
>= 4.00, < 4.94.2CPE matchmatch criteria
cpe:2.3:a:exim:exim:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

9.8CRITICAL

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
5.9
CvssVersion
3.1

Exploit Intelligence

EPSS Score
4.15%
Probability of exploitation in next 30 days
EPSS Percentile
89.8%
Percentile rank of EPSS score among Peer Group
As of 2026-07-28
Model: v2026.06.15
This CVE's current EPSS score of 0.0415 is in the 83rd percentile among its peer group of 36,897 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.

Media Mentions

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Remediation records are not available for this CVE.

References

exim.org / static/doc/security/CVE-2020-qualys/CVE-2020-28024-UNGET.txt
Third Party Advisory