Skip to content
Fencer Vulns
medium 6.4

CVE-2026-106491 json

Backstage: Improper input validation in proxy-backend

published 2026-10-06 33 d ago modified 2026-10-22 17 d ago also GHSA-9ghw-48h5-v2w5 , EUVD-2026-94010

cvss
6.4
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 19%
public exploits
0
none known

Summary

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.

Patch / fix

  • npm @backstage/plugin-proxy-backend 0.6.17
  • linuxfoundation backstage/plugin-proxy-backend 0.6.17
  • linuxfoundation backstage 1.54.6

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-106491 updated cvss 5.4

plugin-proxy-backend: plugin-proxy-backend: Request forwarding outside configured base path via crafted URL

  • Red Hat Developer Hub 1 rhdh/rhdh-hub-rhel9 Red Hat Self-service automation portal 2 ansible-automation-platform/automation-portal, ansible-automation-platform/bootc-automation-portal-rhel9
    affected: workaround, no fix available “Fix deferred”

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
32 d ago

Exploit prediction

0.27% chance of exploitation in the next 30 days, higher than 19% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 6.4 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N
GitHub 3.1 6.4 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N

Affected packages

ecosystem package affected fixed in
npm @backstage/plugin-proxy-backend
<0.6.17
0.6.17

Affected products

  • backstage backstage
  • @backstage plugin-proxy-backend

Classification

Weakness
  • CWE-20 Improper Input Validation
  • CWE-22 Improper Limitation of a Pathname to a Restricted Directory

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.