# CVE-2026-58491: Warpgate: Reflected XSS in SSO return endpoint via attacker-controlled next parameter

> Attackers can execute arbitrary JavaScript in authenticated Warpgate sessions via a crafted SSO link, potentially stealing session data or hijacking accounts.

- **Severity:** Critical 9.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/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:** 21 Sep 2026
- **Updated:** 22 Sep 2026
- **Also known as:** GHSA-3c3w-75j2-7h74

## What is CVE-2026-58491?

CVE-2026-58491 is a critical cross-site scripting vulnerability in warp-tech warpgate, published on 21 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

Warpgate is an open source SSH, HTTPS and MySQL bastion host for Linux. Prior to 0.25.5, the /@warpgate/api/sso/providers/:name/start endpoint stores an attacker-controlled next parameter that the POST /@warpgate/api/sso/return handler inserts without HTML escaping into the response generated by warpgate-protocol-http/src/api/sso_provider_list.rs. A victim who follows a crafted link and completes SSO can cause markup and JavaScript to execute in the authenticated Warpgate origin, allowing access to session data and actions through user APIs, and through administrator APIs only when the victim is an administrator. The GET /@warpgate/api/sso/return path also uses the same unvalidated value as a redirect destination, enabling an open redirect. This issue is fixed in version 0.25.5.

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

## Which versions are affected by CVE-2026-58491?


## How do I fix CVE-2026-58491?

No fix has been published for CVE-2026-58491 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-58491 being exploited?

There is no known exploitation of CVE-2026-58491 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-58491 and fix it if it is affected.

What it is: CVE-2026-58491 is a critical cross-site scripting vulnerability in warp-tech warpgate, published on 21 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-2026-58491 in the wild and no public exploit code.

Affected product: warp-tech warpgate. 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-2026-58491/ (Markdown: https://insights.sbomify.com/CVE-2026-58491/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-58491
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-58491
- OSV: https://osv.dev/vulnerability/CVE-2026-58491

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-58491/
Summaries are generated and may contain mistakes; the official description above is the record.