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 dem…

published 2020-04-24 6 y ago modified 2026-06-17 4 mo ago also EUVD-2020-4379

cvss: 5.3; version 3.1, NVD
cisa kev: Not listed; not in CISA's catalog
epss: 0.9%; EPSS 0.9% chance of exploitation in 30 days, percentile 61%
public exploits: 0; none known

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

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2020-12063 updated 2026-11-07 cvss 0.0

postfix: an attacker may send an email from an arbitrary-looking sender via a homoglyph attack

Red Hat Enterprise Linux 5 postfix Red Hat Enterprise Linux 6 postfix, postfix-perl-scripts Red Hat Enterprise Linux 7 postfix, postfix-sysvinit, postfix-perl-scripts Red Hat Enterprise Linux 8 postfix, postfix-cdb, postfix-ldap, postfix-pcre, postfix-mysql, postfix-pgsql, +2 more
not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

0.94% chance of exploitation in the next 30 days, higher than 61% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

openwall.com https://www.openwall.com/lists/oss-security/2020/04/23/12 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
NVD	3.1	5.3	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
NVD	2.0	5.0	AV:N/AC:L/Au:N/C:N/I:P/A:N

References

openwall.com /lists/oss-security/2020/04/23/12
exploit, mailing-list, third-party-advisory
openwall.com /lists/oss-security/2020/04/23/3
mailing-list, third-party-advisory

Sources

CVE List CVE-2020-12063
NVD CVE-2020-12063

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary