# CVE-2026-73191: Apache Syncope: CAS service URL injection via Forwarded HTTP headers

> Attackers can redirect users to malicious sites via crafted HTTP headers when CAS authentication is enabled in Apache Syncope.

- **Severity:** Medium 6.1 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N`)
- **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:** No
- **Published:** 14 Sep 2026
- **Updated:** 14 Sep 2026
- **Also known as:** GHSA-f668-p5f8-gcxm

## What is CVE-2026-73191?

CVE-2026-73191 is a medium-severity vulnerability in Apache Syncope, published on 14 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

URL Redirection to Untrusted Site ('Open Redirect') vulnerability in Apache Syncope.

When the Syncope SRA is configured for CAS authentication, the target Apereo CAS instance's URL is calculated by unconditionally looking at client-supplied forwarded HTTP headers.

This issue affects Apache Syncope: from 3.0.0-M0 through 3.0.16, from 4.0.0-M0 Through 4.0.7, from 4.1.0-M0 through 4.1.2.

Users are recommended to upgrade to version 4.0.8 / 4.1.3, which fix this issue.

Weakness: CWE-601 (URL Redirection to Untrusted Site)

## Which versions are affected by CVE-2026-73191?


## How do I fix CVE-2026-73191?

No fix has been published for CVE-2026-73191 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-73191 being exploited?

There is no known exploitation of CVE-2026-73191 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-73191 and fix it if it is affected.

What it is: CVE-2026-73191 is a medium-severity vulnerability in Apache Syncope, published on 14 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.
Exploitation: There is no known exploitation of CVE-2026-73191 in the wild and no public exploit code.

Affected product: Apache Syncope. 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-2026-73191/ (Markdown: https://insights.sbomify.com/CVE-2026-73191/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-73191
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-73191
- OSV: https://osv.dev/vulnerability/CVE-2026-73191

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-73191/
Summaries are generated and may contain mistakes; the official description above is the record.