# CVE-2026-107889: Keycloak-services: keycloak-services: stored xss on login page via kcsanitize bypass

> A stored XSS vulnerability in Keycloak's login page allows realm administrators to inject malicious scripts, potentially compromising user sessions and data.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:L/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 9 Oct 2026
- **Updated:** 13 Oct 2026
- **Also known as:** GHSA-gv8g-wx99-6r59

## What is CVE-2026-107889?

CVE-2026-107889 is a medium-severity cross-site scripting vulnerability in Red Hat Build of Keycloak, published on 9 Oct 2026. An attacker needs administrator access to exploit it, with no action from the victim.

### Official description

A flaw was found in the login theme rendering component of Keycloak. The issue occurs because the security filter responsible for cleaning user input can be bypassed, allowing a realm administrator to store malicious scripts in display fields. This could result in unauthorized JavaScript execution in the browsers of users visiting the login page, potentially leading to data exposure or session interference.

Weakness: CWE-79 (Improper Neutralization of Input During Web Page Generation)

## Which versions are affected by CVE-2026-107889?


## How do I fix CVE-2026-107889?

No fix has been published for CVE-2026-107889 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-107889 being exploited?

There is no known exploitation of CVE-2026-107889 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-107889 and fix it if it is affected.

What it is: CVE-2026-107889 is a medium-severity cross-site scripting vulnerability in Red Hat Build of Keycloak, published on 9 Oct 2026. An attacker needs administrator access to exploit it, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-107889 in the wild and no public exploit code.

Affected product: Red Hat Build of Keycloak. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-107889/ (Markdown: https://insights.sbomify.com/CVE-2026-107889/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-107889
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-107889
- OSV: https://osv.dev/vulnerability/CVE-2026-107889

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-107889/
Summaries are generated and may contain mistakes; the official description above is the record.