# CVE-2026-9087: Keycloak: cross-session email verification proof not bound to upstream identity in first-broker-login

> Attackers can link a second upstream identity to a victim's local account by reusing cross-session verification proofs, leading to account takeover.

- **Severity:** Medium 6.4 (`CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 20 May 2026
- **Updated:** 3 Aug 2026
- **Also known as:** ECHO-b2e2-7f87-b426, GHSA-m6qj-3mpp-57v8, MINI-7r72-f98m-fxc6, MINI-wgc3-wr2v-qc67

## What is CVE-2026-9087?

CVE-2026-9087 is a medium-severity authentication bypass vulnerability in Redhat Build of Keycloak, published on 20 May 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.

### Official description

A flaw was found in Keycloak. The cross-session verification proof is keyed only by (local userId,
idpAlias) and is not bound to the upstream identity that was actually verified, so a second upstream account on the same IdP can consume it and get linked to the victim's local account.

Weakness: CWE-639 (Authorization Bypass Through User-Controlled Key)

## Which versions are affected by CVE-2026-9087?

2 open source packages ship an affected version, including org.keycloak:keycloak-services. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `org.keycloak:keycloak-services` | Maven | All versions | 26.6.3 |
| `org.keycloak:keycloak-services` | Maven | All versions | 26.6.3 |

Products: Redhat Build of Keycloak.

## How do I fix CVE-2026-9087?

Upgrade org.keycloak:keycloak-services to 26.6.3 or later.

## Is CVE-2026-9087 being exploited?

There is no known exploitation of CVE-2026-9087 in the wild and no public exploit code.

## Other vulnerabilities in Redhat Build of Keycloak

- [CVE-2026-15572](https://insights.sbomify.com/CVE-2026-15572/): Keycloak-services: keycloak-services: dcr protocol mapper type-swap policy bypass allows privilege escalation (high 8.8)
- [CVE-2026-3047](https://insights.sbomify.com/CVE-2026-3047/): Keycloak SAML Broken has Authentication Bypass by Primary Weakness (high 8.8)
- [CVE-2026-15573](https://insights.sbomify.com/CVE-2026-15573/): Keycloak-services: keycloak-services: authorization bypass via unnormalized uri matching in pathmatcher (high 8.1)
- [CVE-2026-16102](https://insights.sbomify.com/CVE-2026-16102/): Keycloak-services: keycloak-services: default dcr policy allows role forgery via user property mappers (high 8.1)
- [CVE-2026-1609](https://insights.sbomify.com/CVE-2026-1609/): Org.keycloak/keycloak-quarkus-server: keycloak: unauthorized access via jwt authorization grant with disabled users (high 8.1)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-9087 and fix it if it is affected.

What it is: CVE-2026-9087 is a medium-severity authentication bypass vulnerability in Redhat Build of Keycloak, published on 20 May 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-9087 in the wild and no public exploit code.

Affected packages and fixed versions:
- org.keycloak:keycloak-services (Maven): affected all versions; fixed in 26.6.3
- org.keycloak:keycloak-services (Maven): affected all versions; fixed in 26.6.3

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-2026-9087/ (Markdown: https://insights.sbomify.com/CVE-2026-9087/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-9087
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-9087
- OSV: https://osv.dev/vulnerability/CVE-2026-9087

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-9087/
Summaries are generated and may contain mistakes; the official description above is the record.