How severe is CVE-2020-12063?

CVE-2020-12063 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity low, and availability none.

Is CVE-2020-12063 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (56th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2020-12063?

CVE-2020-12063 affects Postfix. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2020-12063?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2020-12063 published?

CVE-2020-12063 was published on 2020-04-24 and last updated on 2026-06-17.

CVE-2020-12063

CVE-2020-12063 is a medium-severity vulnerability in Postfix with a CVSS 3.x base score of 5.3. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low.

Key facts

Severity: Medium (CVSS 3.x base score 5.3)
CVSS v2: 5.0
EPSS exploit prediction: 1% (56th percentile)
Actively exploited: Not listed in CISA KEV
Affected product: Postfix
Published: 2020-04-24
Last modified: 2026-06-17

Description

A certain Postfix 2.10.1-7 package could allow an attacker to send an email from an arbitrary-looking sender via a homoglyph attack, as demonstrated by the similarity of \xce\xbf to the 'o' character. This is potentially relevant when the /etc/postfix/sender_login feature is used, because a spoofed outbound message that uses a configured sender address is blocked with a "Sender address rejected: not logged in" error message, but a spoofed outbound message that uses a homoglyph of a configured sender address is not blocked. NOTE: some third parties argue that any missed blocking of spoofed outbound messages - except for exact matches to a sender address in the /etc/postfix/sender_login file - is outside the design goals of Postfix and thus cannot be considered a Postfix vulnerability

Frequently asked questions

What is CVE-2020-12063?: A certain Postfix 2.10.1-7 package could allow an attacker to send an email from an arbitrary-looking sender via a homoglyph attack, as demonstrated by the similarity of \xce\xbf to the 'o' character. This is potentially relevant when the /etc/postfix/sender_login feature is used, because a spoofed outbound message that uses a configured sender address is blocked with a "Sender address rejected: not logged in" error message, but a spoofed outbound message that uses a homoglyph of a configured sender address is not blocked. NOTE: some third parties argue that any missed blocking of spoofed outbound messages - except for exact matches to a sender address in the /etc/postfix/sender_login file - is outside the design goals of Postfix and thus cannot be considered a Postfix vulnerability
How severe is CVE-2020-12063?: CVE-2020-12063 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity low, and availability none.
Is CVE-2020-12063 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (56th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2020-12063?: CVE-2020-12063 affects Postfix. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2020-12063?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2020-12063 published?: CVE-2020-12063 was published on 2020-04-24 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:postfix:postfix:2.10.1:*:*:*:*:*:*:*