CVE-2020-1758: A flaw was found in Keycloak in versions before 10.0.0, where it does not perform the TLS hostname verificatio

Routine

MEDIUM 5.3WATCHLISTUPGRADEDOWNGRADE

CVE-2020-1758 is a medium-severity flaw (CVSS 5.3) affecting keycloak, openstack. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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.

Why this priority

On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	5.3 (Medium)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	None
User interaction	Required
EPSS exploit chance	0.9% (top 39%)
CISA exploited list	No
Weakness	CWE-297, CWE-295
Published	2020-05-15
Last modified	2026-06-17

Publisher (CNA): Red Hat, Inc. · Vendor: redhat

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2020-05-15 19:15 UTCPublished CVE record published
2026-06-17 03:02 UTCUpdated Record last modified

redhat keycloak UPGRADE

Affected: < 10.0.0

Fixed in: 10.0.0

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy keycloak || rpm -q keycloak || keycloak --version

2. UPGRADE to 10.0.0 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade keycloak

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade keycloak

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

redhat openstack DOWNGRADE

Affected: 10

Fixed in: no fixed release known

Safe to downgrade to: a release before 10

1. Check installed version

apt-cache policy openstack || rpm -q openstack || openstack --version

2. No fixed release: DOWNGRADE to a release before 10 (Debian / Ubuntu)

apt-cache madison openstack sudo apt install openstack=<VERSION_BEFORE_10> sudo apt-mark hold openstack

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list openstack sudo dnf downgrade openstack-<VERSION_BEFORE_10> sudo dnf versionlock add openstack

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2020-1758?

keycloak: upgrade to 10.0.0; openstack: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2020-1758 being exploited?

CVE-2020-1758 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2020-1758 affect?

CVE-2020-1758 affects keycloak, openstack. Severity is medium (CVSS 5.3). 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.

How urgent is CVE-2020-1758?

Priority 39/100. On your watchlist

Software pages

Keycloak vulnerabilities · OpenStack vulnerabilities

Related CVEs

CVE-2023-6927 MEDIUM 4.6 MITIGATE DOWNGRADE A flaw was found in Keycloak
CVE-2023-6563 HIGH 7.7 UPGRADE DOWNGRADE An unconstrained memory consumption vulnerability was discovered in Keycloak
CVE-2023-6291 HIGH 7.1 UPGRADE DOWNGRADE A flaw was found in the redirect_uri validation logic in Keycloak
CVE-2023-6134 MEDIUM 4.6 UPGRADE UPGRADE A flaw was found in Keycloak that prevents certain schemes in redirects, but permits them if a wildcard is app
CVE-2025-8419 MEDIUM 5.3 MITIGATE A vulnerability was found in Keycloak-services

References

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