CVE-2017-12158: It was found that Keycloak would accept a HOST header URL in the admin console and use it to determine web res

This month

MEDIUM 5.4WATCHLISTDOWNGRADEMITIGATE

CVE-2017-12158 is a medium-severity flaw (CVSS 5.4) affecting single sign on, keycloak. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

It was found that Keycloak would accept a HOST header URL in the admin console and use it to determine web resource locations. An attacker could use this flaw against an authenticated user to attain reflected XSS via a malicious server.

Why this priority

On your watchlist

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	5.4 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	Required
EPSS exploit chance	1.0% (top 37%)
CISA exploited list	No
Weakness	CWE-444, CWE-79
Published	2017-10-26
Last modified	2026-06-17

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

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

Am I affected?

Timeline

2017-10-26 17:29 UTCPublished CVE record published
2026-06-17 01:02 UTCUpdated Record last modified

redhat single sign on DOWNGRADE

Affected: 7.0 · 7.1

Fixed in: no fixed release known

Safe to downgrade to: a release before 7.0

1. Check installed version

apt-cache policy single-sign-on || rpm -q single-sign-on || single-sign-on --version

2. No fixed release: DOWNGRADE to a release before 7.0 (Debian / Ubuntu)

apt-cache madison single-sign-on sudo apt install single-sign-on=<VERSION_BEFORE_7.0> sudo apt-mark hold single-sign-on

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

dnf --showduplicates list single-sign-on sudo dnf downgrade single-sign-on-<VERSION_BEFORE_7.0> sudo dnf versionlock add single-sign-on

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.

keycloak keycloak MITIGATE

Affected: all versions

Fixed in: no fixed release known

Safe to downgrade to: no unaffected older release

1. Check installed version

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

No fixed or unaffected release known

Apply the vendor mitigation from the advisory, disable the affected feature, or restrict network access.

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-2017-12158?

single sign on: downgrade or apply the listed mitigation; keycloak: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2017-12158 being exploited?

CVE-2017-12158 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-2017-12158 affect?

CVE-2017-12158 affects single sign on, keycloak. Severity is medium (CVSS 5.4). It was found that Keycloak would accept a HOST header URL in the admin console and use it to determine web resource locations. An attacker could use this flaw against an authenticated user to attain reflected XSS via a malicious server.

How urgent is CVE-2017-12158?

Priority 40/100. On your watchlist

Software pages

Keycloak vulnerabilities

Related CVEs

CVE-2017-2585 MEDIUM 5.9 UPGRADE DOWNGRADE Red Hat Keycloak before version 2.5.1 has an implementation of HMAC verification for JWS tokens that uses a me
CVE-2017-12159 HIGH 7.5 DOWNGRADE MITIGATE It was found that the cookie used for CSRF prevention in Keycloak was not unique to each session
CVE-2016-8629 MEDIUM 6.5 UPGRADE DOWNGRADE Red Hat Keycloak before version 2.4.0 did not correctly check permissions when handling service account user d

References

← Back to latest CVEs