CVE-2026-44203 OpenAM: Pre-auth Reflected XSS in OAuth2 / OIDC response_mode=form_post via state parameter (FormPostResponse.ftl)
An unauthenticated attacker can execute arbitrary script in the OpenAM origin via a crafted OAuth2 authorization request, potentially leading to account takeover.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-44203?
CVE-2026-44203 is a high-severity cross-site scripting vulnerability in OpenIdentityPlatform OpenAM, published on 15 Sep 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
Open Access Management (OpenAM) is an access management solution. Prior to 16.1.1, the OAuth 2.0 and OpenID Connect authorization endpoint does not sufficiently encode user-supplied parameters before FormPostResponse.ftl and checkSession.ftl render them into HTML for the form_post response mode. An unauthenticated attacker can induce a user to open a crafted authorization request and execute script in the OpenAM origin. This issue is fixed in version 16.1.1.
Weakness: CWE-79
Which versions are affected by CVE-2026-44203?
2 open source packages ship an affected version, including org.openidentityplatform.openam:openam-oauth2.
| Package | Affected | Fixed in |
|---|---|---|
org.openidentityplatform.openam:openam-oauth2 Maven | From 13.0.0 | 16.1.1 |
org.openidentityplatform.openam:openam-oauth2 Maven | From 13.0.0 | 16.1.1 |
How do I fix CVE-2026-44203?
Upgrade org.openidentityplatform.openam:openam-oauth2 to 16.1.1 or later.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-44203 being exploited?
There is no known exploitation of CVE-2026-44203 in the wild and no public exploit code.
Sources
Also known as GHSA-fq9h-c788-fx73, UBUNTU-CVE-2026-44203.