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CVE-2026-106491— Backstage: Improper input validation in proxy-backend

Quick assessment

Affected
backstage backstage
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Backstage 是一个用于构建开发者门户的开源框架。在版本 0.6.17 之前， 包存在代理后端输入验证不当的问题。经过身份验证的 Backstage 用户可以构造一个请求 URL，导致代理后端将请求转发到目标服务器上配置的基本路径之外的路径。该漏洞仅限于已配置为代理端点的目标服务器，并且默认需要 Backstage 身份验证。此问题已在 0.6.17 版本中修复。

CVSS 6.4 · Medium
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I. Basic Information for CVE-2026-106491

Vulnerability Information
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Vulnerability Title
Backstage: Improper input validation in proxy-backend
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
输入验证不恰当
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
backstage backstage < 1.54.6 -
@backstage plugin-proxy-backend < 0.6.17 -

II. Public POCs for CVE-2026-106491

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III. Intelligence Information for CVE-2026-106491

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Vendor Pages for CVE-2026-106491 (1)

Other References for CVE-2026-106491 (2)

Same Patch Batch · backstage · 2026-10-06 · 18 CVEs total

CVE-2026-106486 8.5 HIGH Backstage: Improper filesystem validation in Bitbucket pull-request scaffolder actions
CVE-2026-106459 8.5 HIGH Backstage: Improper input validation in Sentry scaffolder actions
CVE-2026-106488 8.1 HIGH Backstage: Improper authentication in the OIDC provider
CVE-2026-106455 7.7 HIGH Backstage: Improper validation of MkDocs plugin configuration in TechDocs
CVE-2026-106492 7.6 HIGH Backstage: Improper preservation of access restrictions during service credential delegati
CVE-2026-106460 6.8 MEDIUM Backstage: Explicit negative email verification can be ignored during shared OAuth profile
CVE-2026-106457 6.8 MEDIUM Backstage: Insufficient audience validation in the Cloudflare Access auth provider
CVE-2026-106458 6.5 MEDIUM Backstage: Inconsistent repository filtering in Bitbucket Server catalog event updates
CVE-2026-106490 6.5 MEDIUM Backstage: Improper input validation in TechDocs static content requests
CVE-2026-106489 6.5 MEDIUM Backstage: Improper authorization enforcement for TechDocs static content
CVE-2026-106462 6.4 MEDIUM Backstage: Scaffolder credential handling may allow unintended GitHub authentication fallb
CVE-2026-106463 5.4 MEDIUM Backstage: Improper authorization in GitLab organizational user ingestion
CVE-2026-106456 4.8 MEDIUM Backstage: Inconsistent credential enforcement for overlapping proxy routes
CVE-2026-106494 4.4 MEDIUM Backstage: Improper input validation in cloud storage URL readers
CVE-2026-106461 4.3 MEDIUM Backstage: Incorrect authorization in scaffolder task listing
CVE-2026-106487 3.5 LOW Backstage: Unsupported catalog cluster authentication mode in kubernetes backend
CVE-2026-106493 3.0 LOW Backstage: Cloud storage catalog locations may cross configured storage boundaries

IV. Related Vulnerabilities

Same product: backstage
Same vendor: backstage
Same weakness: CWE-20

V. Comments for CVE-2026-106491

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