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Fencer Vulns
medium 5.3

CVE-2020-1758 json

Improper Certificate Validation and Improper Validation of Certificate with Host Mismatch in Keycloak

published 2020-05-15 6 y ago modified 2026-06-17 4 mo ago also GHSA-c597-f74m-jgc2 , EUVD-2022-0953

cvss
5.3
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.9%
EPSS 0.9% chance of exploitation in 30 days, percentile 60%
public exploits
0
none known

Summary

A flaw was found in Keycloak in versions before 10.0.0, where it does not perform the TLS hostname verification while sending emails using the SMTP server. This flaw allows an attacker to perform a man-in-the-middle (MITM) attack.

Patch / fix

  • maven org.keycloak:keycloak-parent 10.0.0
  • redhat keycloak 10.0.0
  • rh-sso7-keycloak red hat single sign on 7 4.8.20-1.Final_redhat_00001.1.el8sso
  • rh-sso7-keycloak-server red hat single sign on 7 4.8.20-1.Final_redhat_00001.1.el8sso
  • rh-sso7-keycloak red hat single sign on 7 4.8.20-1.Final_redhat_00001.1.el7sso
  • rh-sso7-keycloak-server red hat single sign on 7 4.8.20-1.Final_redhat_00001.1.el7sso
  • rh-sso7-keycloak red hat single sign on 7 4.8.20-1.Final_redhat_00001.1.el6sso
  • rh-sso7-keycloak-server red hat single sign on 7 4.8.20-1.Final_redhat_00001.1.el6sso

red hat advisories RHSA-2020:2108RHSA-2020:2107RHSA-2020:2106

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-2020-1758 updated cvss 5.3

keycloak: improper verification of certificate with host mismatch could result in information disclosure

  • Red Hat OpenStack Platform 10 (Newton) keycloak-httpd-client-install
    affected: workaround, no fix planned “Turn off all kinds of email notifications including password reset mails.”
  • Red Hat Single Sign On 7.3.8
    fixed: vendor fix “Turn off all kinds of email notifications including password reset mails.” RHSA-2020:2112
  • Red Hat Single Sign-On 7.3 for RHEL 6 Server rh-sso7-keycloak 4.8.20-1.Final_redhat_00001.1.el6sso, rh-sso7-keycloak-server 4.8.20-1.Final_redhat_00001.1.el6sso
    fixed: vendor fix “Turn off all kinds of email notifications including password reset mails.” RHSA-2020:2106
  • Red Hat Single Sign-On 7.3 for RHEL 7 Server rh-sso7-keycloak 4.8.20-1.Final_redhat_00001.1.el7sso, rh-sso7-keycloak-server 4.8.20-1.Final_redhat_00001.1.el7sso
    fixed: vendor fix “Turn off all kinds of email notifications including password reset mails.” RHSA-2020:2107
  • Red Hat Single Sign-On 7.3 for RHEL 8 rh-sso7-keycloak 4.8.20-1.Final_redhat_00001.1.el8sso, rh-sso7-keycloak-server 4.8.20-1.Final_redhat_00001.1.el8sso
    fixed: vendor fix “Turn off all kinds of email notifications including password reset mails.” RHSA-2020:2108
  • Red Hat Fuse 7 keycloak keycloak Red Hat OpenShift Application Runtimes keycloak keycloak Red Hat support for Spring Boot keycloak keycloak
    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

0.93% chance of exploitation in the next 30 days, higher than 60% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 5.3 CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:N/A:N
NVD 3.1 5.9 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
NVD 2.0 4.3 AV:N/AC:M/Au:N/C:P/I:N/A:N
GitHub 3.1 5.9 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

Affected packages

ecosystem package affected fixed in
maven org.keycloak:keycloak-parent
<10.0.0
10.0.0

Affected products

  • Red Hat keycloak

Classification

Weakness
  • CWE-297 Improper Validation of Certificate with Host Mismatch
  • CWE-295 Improper Certificate Validation

References

Sources

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.