CVE-2026-106491 Backstage: Improper input validation in proxy-backend
Authenticated users can bypass proxy restrictions to access unauthorized paths on configured target servers in Backstage.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-106491?
CVE-2026-106491 is a medium-severity path traversal vulnerability in Linuxfoundation Backstage, published on 6 Oct 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
Backstage is an open framework for building developer portals. Prior to 0.6.17, the @backstage/plugin-proxy-backend package is affected by improper input validation in proxy-backend. An authenticated Backstage user could craft a request URL that causes the proxy-backend to forward the request to a path outside the configured base path on the target server. This is limited to target servers already configured as proxy endpoints and requires Backstage authentication by default. This issue is fixed in version 0.6.17.
Which versions are affected by CVE-2026-106491?
2 open source packages ship an affected version, including @backstage/plugin-proxy-backend. It affects 2 products.
| Package | Affected | Fixed in |
|---|---|---|
@backstage/plugin-proxy-backend npm | All versions | 0.6.17 |
@backstage/plugin-proxy-backend npm | All versions | 0.6.17 |
Products include Linuxfoundation Backstage, Linuxfoundation Backstage\/Plugin-Proxy-Backend.
How do I fix CVE-2026-106491?
Upgrade @backstage/plugin-proxy-backend to 0.6.17 or later.
Upgrade, and resolve every user-supplied path against an allowed base folder before opening it. More about Path traversal.
Is CVE-2026-106491 being exploited?
There is no known exploitation of CVE-2026-106491 in the wild and no public exploit code.
Other vulnerabilities in Linuxfoundation Backstage
- CVE-2026-106501 Backstage: Sensitive information exposure in Scaffolder
- CVE-2026-106558 Backstage: Improper validation of TechDocs MkDocs configuration
- CVE-2026-88064 Backstage: Improper input validation in TechDocs MkDocs configuration
- CVE-2026-106459 Backstage: Improper input validation in Sentry scaffolder actions
- CVE-2026-106486 Backstage: Improper filesystem validation in Bitbucket pull-request scaffolder actions
Sources
Also known as GHSA-9ghw-48h5-v2w5.