CVE-2026-3872: A flaw was found in Keycloak

This month

HIGH 7.3WATCHLISTDOWNGRADE

CVE-2026-3872 is a high-severity flaw (CVSS 7.3) 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 Keycloak. This issue allows an attacker, who controls another path on the same web server, to bypass the allowed path in redirect Uniform Resource Identifiers (URIs) that use a wildcard. A successful attack may lead to the theft of an access token, resulting in information disclosure.

Why this priority

High severity
On your watchlist

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

Risk facts

CVSS score	7.3 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	Required
EPSS exploit chance	0.4% (top 62%)
CISA exploited list	No
Weakness	CWE-601
Published	2026-04-02
Last modified	2026-10-26

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

Last updated 2026-10-26 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-04-02 13:16 UTCPublished CVE record published
2026-10-26 21:10 UTCUpdated Record last modified

redhat build of keycloak DOWNGRADE

Affected: all versions · 26.2 · 26.2.15 · 26.4 · 26.4.11

Fixed in: no fixed release known

Safe to downgrade to: a release before 26.2

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 26.2 (Debian / Ubuntu)

apt-cache madison build-of-keycloak sudo apt install build-of-keycloak=<VERSION_BEFORE_26.2> sudo apt-mark hold build-of-keycloak

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

dnf --showduplicates list build-of-keycloak sudo dnf downgrade build-of-keycloak-<VERSION_BEFORE_26.2> 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-2026-3872?

build of keycloak: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2026-3872 being exploited?

CVE-2026-3872 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-2026-3872 affect?

CVE-2026-3872 affects build of keycloak. Severity is high (CVSS 7.3). A flaw was found in Keycloak. This issue allows an attacker, who controls another path on the same web server, to bypass the allowed path in redirect Uniform Resource Identifiers (URIs) that use a wildcard. A successful attack may lead to t

How urgent is CVE-2026-3872?

Priority 40/100. High severity; On your watchlist

Software pages

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-2026-37980 MEDIUM 6.9 MITIGATE A flaw was found in Keycloak, specifically in the organization selection login page
CVE-2026-4325 MEDIUM 5.3 DOWNGRADE A flaw was found in Keycloak

References

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