How severe is CVE-2020-8794?

CVE-2020-8794 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2020-8794 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 89% (100th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2020-8794?

CVE-2020-8794 primarily affects Opensmtpd. In total, 7 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2020-8794?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2020-8794 published?

CVE-2020-8794 was published on 2020-02-25 and last updated on 2026-06-17.

CVE-2020-8794

CVE-2020-8794 is a critical-severity vulnerability in Opensmtpd with a CVSS 3.x base score of 9.8. Its EPSS exploit-prediction score of 89% places it in the 100th percentile, indicating an elevated likelihood of exploitation. The underlying weakness is classified as CWE-125.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 10.0
EPSS exploit prediction: 89% (100th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-125
Affected product: Opensmtpd
Published: 2020-02-25
Last modified: 2026-06-17

Description

OpenSMTPD before 6.6.4 allows remote code execution because of an out-of-bounds read in mta_io in mta_session.c for multi-line replies. Although this vulnerability affects the client side of OpenSMTPD, it is possible to attack a server because the server code launches the client code during bounce handling.

Frequently asked questions

What is CVE-2020-8794?: OpenSMTPD before 6.6.4 allows remote code execution because of an out-of-bounds read in mta_io in mta_session.c for multi-line replies. Although this vulnerability affects the client side of OpenSMTPD, it is possible to attack a server because the server code launches the client code during bounce handling.
How severe is CVE-2020-8794?: CVE-2020-8794 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2020-8794 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 89% (100th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2020-8794?: CVE-2020-8794 primarily affects Opensmtpd. In total, 7 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2020-8794?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2020-8794 published?: CVE-2020-8794 was published on 2020-02-25 and last updated on 2026-06-17.

References

Affected products (7)

cpe:2.3:a:opensmtpd:opensmtpd:*:*:*:*:*:*:*:*
cpe:2.3:o:canonical:ubuntu_linux:18.04:*:*:*:lts:*:*:*
cpe:2.3:o:canonical:ubuntu_linux:19.10:*:*:*:*:*:*:*
cpe:2.3:o:fedoraproject:fedora:31:*:*:*:*:*:*:*
cpe:2.3:o:fedoraproject:fedora:32:*:*:*:*:*:*:*
cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*
cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*

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Other CWE-125 (Out-of-bounds Read) vulnerabilities

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CVE-2021-41556 — Critical (CVSS 10.0): sqclass.cpp in Squirrel through 2.2.5 and 3.x through 3.1 allows an out-of-bounds read (in the core interpreter) that…
CVE-2021-21777 — Critical (CVSS 10.0): An information disclosure vulnerability exists in the Ethernet/IP UDP handler functionality of EIP Stack Group OpENer…
CVE-2017-14451 — Critical (CVSS 10.0): An exploitable out-of-bounds read vulnerability exists in libevm (Ethereum Virtual Machine) of CPP-Ethereum. A…
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