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LOW severity

Keycloak's improper input validation allows using email as usernameGHSA-4vc8-pg5c-vg4x

LOWFix: keycloak/keycloak@f970803

GHSA-4vc8-pg5c-vg4x is a low-severity (CVSS 3.7) Improper Input Validation vulnerability in org.keycloak:keycloak-services. A fix is available for org.keycloak:keycloak-services — see the affected versions and patch details below.

Also known asCVE-2021-3754
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Nov 5, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
2.2%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs83th percentile — riskier than 83% of all scored CVEsHighest risk
0.00%5.15%10.3%15.5%12.3%2.2%May 26Sep 26Nov 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected
☕org.keycloak:keycloak-services

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.

Description

Keycloak allows the use of email as a username and doesn't check that an account with this email already exists. That could lead to the unability to reset/login with email for the user. This is caused by usernames being evaluated before emails.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
☕Mavenorg.keycloak:keycloak-servicesall versions24.0.1org.keycloak:keycloak-services:24.0.1

Affected Products

2 products · 2 configurations
Application
keycloakredhat
all
Application
single sign-onredhat
1 version
7.0

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.keycloak:keycloak-services, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update org.keycloak:keycloak-services to 24.0.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-4vc8-pg5c-vg4x is resolved across your whole dependency graph.

  3. Workarounds

    If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatLow
Workaround published by Red Hat
The workaround is to enable "Email as username" flag or disable "Login with email" in the login settings
Source: Red Hat security advisory for GHSA-4vc8-pg5c-vg4x (CC BY 4.0)

Frequently Asked Questions

Keycloak allows the use of email as a username and doesn't check that an account with this email already exists. That could lead to the unability to reset/login with email for the user. This is caused by usernames being evaluated before emails.
O3 Security · Impact-Aware SCA

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