CVE-2026-16100: A flaw was found in the user-event metrics recording of Keycloak

Routine

MEDIUM 6.5WATCHLISTUPGRADE

CVE-2026-16100 is a medium-severity flaw (CVSS 6.5) affecting build of keycloak. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A flaw was found in the user-event metrics recording of Keycloak. When metrics are enabled, the system records raw error messages from failed account operations as Prometheus metric labels. Because these error messages can include user-supplied input like nonexistent client IDs, an authenticated user can create a massive number of unique metric entries, eventually exhausting system memory and causing the service to crash or become unavailable.

Why this priority

On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	6.5 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	0.6% (top 54%)
CISA exploited list	No
Weakness	CWE-770
Published	2026-08-05
Last modified	2026-08-31

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

Last updated 2026-08-31 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-08-05 15:16 UTCPublished CVE record published
2026-08-31 12:17 UTCUpdated Record last modified

redhat build of keycloak UPGRADE

Affected: >= 26.6 and < 26.6.5

Fixed in: 26.6.5

Safe to downgrade to: a release before 26.6

1. Check installed version

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

2. UPGRADE to 26.6.5 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade build-of-keycloak

Note

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

3. If no update is available yet, DOWNGRADE to a release before 26.6 (Debian / Ubuntu)

apt-cache madison build-of-keycloak sudo apt install build-of-keycloak=<VERSION_BEFORE_26.6> sudo apt-mark hold build-of-keycloak

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list build-of-keycloak sudo dnf downgrade build-of-keycloak-<VERSION_BEFORE_26.6> sudo dnf versionlock add build-of-keycloak

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-2026-16100?

build of keycloak: upgrade to 26.6.5. Exact commands for each OS are on this page.

Is CVE-2026-16100 being exploited?

CVE-2026-16100 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-2026-16100 affect?

CVE-2026-16100 affects build of keycloak. Severity is medium (CVSS 6.5). A flaw was found in the user-event metrics recording of Keycloak. When metrics are enabled, the system records raw error messages from failed account operations as Prometheus metric labels. Because these error messages can include user-supp

How urgent is CVE-2026-16100?

Priority 39/100. On your watchlist

Software pages

Prometheus vulnerabilities · Keycloak vulnerabilities

Related CVEs

CVE-2026-4634 HIGH 7.5 DOWNGRADE A flaw was found in Keycloak
CVE-2026-4636 HIGH 8.1 DOWNGRADE A flaw was found in Keycloak
CVE-2026-4282 HIGH 7.4 DOWNGRADE A flaw was found in Keycloak
CVE-2026-3872 HIGH 7.3 DOWNGRADE A flaw was found in Keycloak
CVE-2026-37980 MEDIUM 6.9 MITIGATE A flaw was found in Keycloak, specifically in the organization selection login page

References

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